[TTI] Improved cost heuristic for cttz/ctlz calls.
This patch is a follow-up of r228826 (see code-review: D7506). Now that SimplifyCFG uses TargetTransformInfo for cost analysis, we have to fix the cost heuristic for intrinsic calls to cttz/ctlz. This patch defines method 'getIntrinsicCost' in BasicTTIImpl: now, BasicTTIImpl queries TLI to check if a call to cttz/ctlz is cheap for the target. Added test cases in Transforms/SimplifyCFG/X86 to verify that on x86, SimplifyCFG only speculates a call to cttz/ctlz if it is cheap. Differential Revision: http://reviews.llvm.org/D7554 llvm-svn: 228829
This commit is contained in:
Andrea Di Biagio
parent
cb527a7fcd
commit
2a0e435db1
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@ -150,6 +150,28 @@ public:
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return getTLI()->isTypeLegal(VT);
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return getTLI()->isTypeLegal(VT);
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}
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}
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unsigned getIntrinsicCost(Intrinsic::ID IID, Type *RetTy,
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ArrayRef<const Value *> Arguments) {
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return BaseT::getIntrinsicCost(IID, RetTy, Arguments);
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}
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unsigned getIntrinsicCost(Intrinsic::ID IID, Type *RetTy,
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ArrayRef<Type *> ParamTys) {
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if (IID == Intrinsic::cttz) {
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if (getTLI()->isCheapToSpeculateCttz())
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return TargetTransformInfo::TCC_Basic;
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return TargetTransformInfo::TCC_Expensive;
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}
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if (IID == Intrinsic::ctlz) {
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if (getTLI()->isCheapToSpeculateCtlz())
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return TargetTransformInfo::TCC_Basic;
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return TargetTransformInfo::TCC_Expensive;
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}
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return BaseT::getIntrinsicCost(IID, RetTy, ParamTys);
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}
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unsigned getJumpBufAlignment() { return getTLI()->getJumpBufAlignment(); }
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unsigned getJumpBufAlignment() { return getTLI()->getJumpBufAlignment(); }
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unsigned getJumpBufSize() { return getTLI()->getJumpBufSize(); }
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unsigned getJumpBufSize() { return getTLI()->getJumpBufSize(); }
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@ -28,22 +28,6 @@ bb3: ; preds = %bb2, %entry
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ret i32 %tmp5
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ret i32 %tmp5
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}
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}
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declare i8 @llvm.cttz.i8(i8, i1)
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define i8 @test2(i8 %a) {
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; CHECK-LABEL: @test2(
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br i1 undef, label %bb_true, label %bb_false
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bb_true:
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%b = tail call i8 @llvm.cttz.i8(i8 %a, i1 false)
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br label %join
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bb_false:
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br label %join
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join:
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%c = phi i8 [%b, %bb_true], [%a, %bb_false]
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; CHECK: select
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ret i8 %c
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}
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define i8* @test4(i1* %dummy, i8* %a, i8* %b) {
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define i8* @test4(i1* %dummy, i8* %a, i8* %b) {
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; Test that we don't speculate an arbitrarily large number of unfolded constant
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; Test that we don't speculate an arbitrarily large number of unfolded constant
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; expressions.
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; expressions.
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@ -0,0 +1,141 @@
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; RUN: opt -S -simplifycfg -mtriple=x86_64-unknown-unknown -mattr=+bmi < %s | FileCheck %s --check-prefix=ALL --check-prefix=BMI
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; RUN: opt -S -simplifycfg -mtriple=x86_64-unknown-unknown -mattr=+lzcnt < %s | FileCheck %s --check-prefix=ALL --check-prefix=LZCNT
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; RUN: opt -S -simplifycfg -mtriple=x86_64-unknown-unknown < %s | FileCheck %s --check-prefix=ALL --check-prefix=GENERIC
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define i64 @test1(i64 %A) {
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; ALL-LABEL: @test1(
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; ALL: [[COND:%[A-Za-z0-9]+]] = icmp eq i64 %A, 0
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; ALL: [[CTLZ:%[A-Za-z0-9]+]] = tail call i64 @llvm.ctlz.i64(i64 %A, i1 true)
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; LZCNT-NEXT: select i1 [[COND]], i64 64, i64 [[CTLZ]]
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; BMI-NOT: select
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; GENERIC-NOT: select
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; ALL: ret
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entry:
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%tobool = icmp eq i64 %A, 0
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br i1 %tobool, label %cond.end, label %cond.true
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cond.true: ; preds = %entry
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%0 = tail call i64 @llvm.ctlz.i64(i64 %A, i1 true)
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br label %cond.end
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cond.end: ; preds = %entry, %cond.true
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%cond = phi i64 [ %0, %cond.true ], [ 64, %entry ]
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ret i64 %cond
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}
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define i32 @test2(i32 %A) {
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; ALL-LABEL: @test2(
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; ALL: [[COND:%[A-Za-z0-9]+]] = icmp eq i32 %A, 0
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; ALL: [[CTLZ:%[A-Za-z0-9]+]] = tail call i32 @llvm.ctlz.i32(i32 %A, i1 true)
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; LZCNT-NEXT: select i1 [[COND]], i32 32, i32 [[CTLZ]]
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; BMI-NOT: select
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; GENERIC-NOT: select
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; ALL: ret
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entry:
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%tobool = icmp eq i32 %A, 0
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br i1 %tobool, label %cond.end, label %cond.true
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cond.true: ; preds = %entry
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%0 = tail call i32 @llvm.ctlz.i32(i32 %A, i1 true)
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br label %cond.end
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cond.end: ; preds = %entry, %cond.true
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%cond = phi i32 [ %0, %cond.true ], [ 32, %entry ]
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ret i32 %cond
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}
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define signext i16 @test3(i16 signext %A) {
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; ALL-LABEL: @test3(
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; ALL: [[COND:%[A-Za-z0-9]+]] = icmp eq i16 %A, 0
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; ALL: [[CTLZ:%[A-Za-z0-9]+]] = tail call i16 @llvm.ctlz.i16(i16 %A, i1 true)
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; LZCNT-NEXT: select i1 [[COND]], i16 16, i16 [[CTLZ]]
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; BMI-NOT: select
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; GENERIC-NOT: select
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; ALL: ret
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entry:
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%tobool = icmp eq i16 %A, 0
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br i1 %tobool, label %cond.end, label %cond.true
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cond.true: ; preds = %entry
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%0 = tail call i16 @llvm.ctlz.i16(i16 %A, i1 true)
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br label %cond.end
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cond.end: ; preds = %entry, %cond.true
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%cond = phi i16 [ %0, %cond.true ], [ 16, %entry ]
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ret i16 %cond
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}
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define i64 @test1b(i64 %A) {
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; ALL-LABEL: @test1b(
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; ALL: [[COND:%[A-Za-z0-9]+]] = icmp eq i64 %A, 0
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; ALL: [[CTTZ:%[A-Za-z0-9]+]] = tail call i64 @llvm.cttz.i64(i64 %A, i1 true)
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; BMI-NEXT: select i1 [[COND]], i64 64, i64 [[CTTZ]]
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; LZCNT-NOT: select
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; GENERIC-NOT: select
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; ALL: ret
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entry:
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%tobool = icmp eq i64 %A, 0
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br i1 %tobool, label %cond.end, label %cond.true
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cond.true: ; preds = %entry
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%0 = tail call i64 @llvm.cttz.i64(i64 %A, i1 true)
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br label %cond.end
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cond.end: ; preds = %entry, %cond.true
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%cond = phi i64 [ %0, %cond.true ], [ 64, %entry ]
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ret i64 %cond
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}
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define i32 @test2b(i32 %A) {
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; ALL-LABEL: @test2b(
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; ALL: [[COND:%[A-Za-z0-9]+]] = icmp eq i32 %A, 0
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; ALL: [[CTTZ:%[A-Za-z0-9]+]] = tail call i32 @llvm.cttz.i32(i32 %A, i1 true)
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; BMI-NEXT: select i1 [[COND]], i32 32, i32 [[CTTZ]]
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; LZCNT-NOT: select
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; GENERIC-NOT: select
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; ALL: ret
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entry:
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%tobool = icmp eq i32 %A, 0
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br i1 %tobool, label %cond.end, label %cond.true
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cond.true: ; preds = %entry
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%0 = tail call i32 @llvm.cttz.i32(i32 %A, i1 true)
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br label %cond.end
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cond.end: ; preds = %entry, %cond.true
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%cond = phi i32 [ %0, %cond.true ], [ 32, %entry ]
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ret i32 %cond
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}
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define signext i16 @test3b(i16 signext %A) {
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; ALL-LABEL: @test3b(
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; ALL: [[COND:%[A-Za-z0-9]+]] = icmp eq i16 %A, 0
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; ALL: [[CTTZ:%[A-Za-z0-9]+]] = tail call i16 @llvm.cttz.i16(i16 %A, i1 true)
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; BMI-NEXT: select i1 [[COND]], i16 16, i16 [[CTTZ]]
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; LZCNT-NOT: select
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; GENERIC-NOT: select
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; ALL: ret
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entry:
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%tobool = icmp eq i16 %A, 0
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br i1 %tobool, label %cond.end, label %cond.true
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cond.true: ; preds = %entry
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%0 = tail call i16 @llvm.cttz.i16(i16 %A, i1 true)
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br label %cond.end
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cond.end: ; preds = %entry, %cond.true
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%cond = phi i16 [ %0, %cond.true ], [ 16, %entry ]
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ret i16 %cond
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}
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declare i64 @llvm.ctlz.i64(i64, i1)
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declare i32 @llvm.ctlz.i32(i32, i1)
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declare i16 @llvm.ctlz.i16(i16, i1)
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declare i64 @llvm.cttz.i64(i64, i1)
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declare i32 @llvm.cttz.i32(i32, i1)
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declare i16 @llvm.cttz.i16(i16, i1)
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