replica
/
hanchenye-llvm-project
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

[SimplifyCFG] don't create a no-op subtract 

I noticed this inefficiency while investigating PR34603:
https://bugs.llvm.org/show_bug.cgi?id=34603

This fix will likely push another bug (we don't maintain state of 'LateSimplifyCFG') 
into hiding, but I'll try to clean that up with a follow-up patch anyway.

llvm-svn: 313829
This commit is contained in:
Sanjay Patel 2017-09-20 22:31:35 +00:00
parent bb8636477d
commit 73811a152a
3 changed files with 21 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -5275,8 +5275,12 @@ static bool SwitchToLookupTable(SwitchInst *SI, IRBuilder<> &Builder,
// Compute the table index value.
Builder.SetInsertPoint(SI);
Value *TableIndex =
Builder.CreateSub(SI->getCondition(), MinCaseVal, "switch.tableidx");
Value *TableIndex;
if (MinCaseVal->isNullValue())
TableIndex = SI->getCondition();
else
TableIndex = Builder.CreateSub(SI->getCondition(), MinCaseVal,
"switch.tableidx");
// Compute the maximum table size representable by the integer type we are
// switching upon.

31
llvm/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
View File

@ -90,14 +90,13 @@ sw.epilog:
; CHECK-LABEL: @h(
; CHECK: entry:
; CHECK-NEXT: %switch.tableidx = sub i32 %x, 0
; CHECK-NEXT: %0 = icmp ult i32 %switch.tableidx, 4
; CHECK-NEXT: %0 = icmp ult i32 %x, 4
; CHECK-NEXT: br i1 %0, label %switch.lookup, label %sw.epilog
; CHECK: switch.lookup:
; CHECK-NEXT: %switch.shiftamt = mul i32 %switch.tableidx, 8
; CHECK-NEXT: %switch.shiftamt = mul i32 %x, 8
; CHECK-NEXT: %switch.downshift = lshr i32 89655594, %switch.shiftamt
; CHECK-NEXT: %switch.masked = trunc i32 %switch.downshift to i8
; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x float], [4 x float]* @switch.table.h, i32 0, i32 %switch.tableidx
; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x float], [4 x float]* @switch.table.h, i32 0, i32 %x
; CHECK-NEXT: %switch.load = load float, float* %switch.gep
; CHECK-NEXT: br label %sw.epilog
; CHECK: sw.epilog:
@ -140,11 +139,10 @@ return:
; CHECK-LABEL: @foostring(
; CHECK: entry:
; CHECK-NEXT: %switch.tableidx = sub i32 %x, 0
; CHECK-NEXT: %0 = icmp ult i32 %switch.tableidx, 4
; CHECK-NEXT: %0 = icmp ult i32 %x, 4
; CHECK-NEXT: br i1 %0, label %switch.lookup, label %return
; CHECK: switch.lookup:
; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x i8*], [4 x i8*]* @switch.table.foostring, i32 0, i32 %switch.tableidx
; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x i8*], [4 x i8*]* @switch.table.foostring, i32 0, i32 %x
; CHECK-NEXT: %switch.load = load i8*, i8** %switch.gep
; CHECK-NEXT: ret i8* %switch.load
}
@ -173,7 +171,7 @@ sw.epilog:
; CHECK-LABEL: @earlyreturncrash(
; CHECK: switch.lookup:
; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x i32], [4 x i32]* @switch.table.earlyreturncrash, i32 0, i32 %switch.tableidx
; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x i32], [4 x i32]* @switch.table.earlyreturncrash, i32 0, i32 %x
; CHECK-NEXT: %switch.load = load i32, i32* %switch.gep
; CHECK-NEXT: ret i32 %switch.load
; CHECK: sw.epilog:
@ -285,7 +283,7 @@ bb3:
%tmp4 = phi i1 [ undef, %bb ], [ false, %bb2 ], [ true, %bb1 ]
ret i1 %tmp4
; CHECK-LABEL: define i1 @undef(
; CHECK: %switch.cast = trunc i32 %switch.tableidx to i9
; CHECK: %switch.cast = trunc i32 %tmp to i9
; CHECK: %switch.downshift = lshr i9 3, %switch.shiftamt
}
@ -778,7 +776,7 @@ return:
; CHECK-LABEL: @unreachable_case(
; CHECK: switch.lookup:
; CHECK: getelementptr inbounds [9 x i32], [9 x i32]* @switch.table.unreachable_case, i32 0, i32 %switch.tableidx
; CHECK: getelementptr inbounds [9 x i32], [9 x i32]* @switch.table.unreachable_case, i32 0, i32 %x
}
define i32 @unreachable_default(i32 %x) {
@ -802,10 +800,9 @@ return:
; CHECK-LABEL: @unreachable_default(
; CHECK: entry:
; CHECK-NEXT: %switch.tableidx = sub i32 %x, 0
; CHECK-NOT: icmp
; CHECK-NOT: br 1i
; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x i32], [4 x i32]* @switch.table.unreachable_default, i32 0, i32 %switch.tableidx
; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x i32], [4 x i32]* @switch.table.unreachable_default, i32 0, i32 %x
; CHECK-NEXT: %switch.load = load i32, i32* %switch.gep
; CHECK-NEXT: ret i32 %switch.load
}
@ -884,7 +881,7 @@ return:
; CHECK: entry:
; CHECK: br i1 %{{.*}}, label %switch.hole_check, label %sw.default
; CHECK: switch.hole_check:
; CHECK-NEXT: %switch.maskindex = trunc i32 %switch.tableidx to i8
; CHECK-NEXT: %switch.maskindex = trunc i32 %c to i8
; CHECK-NEXT: %switch.shifted = lshr i8 47, %switch.maskindex
; The mask is binary 101111.
; CHECK-NEXT: %switch.lobit = trunc i8 %switch.shifted to i1
@ -915,11 +912,10 @@ return:
define i32 @threecases(i32 %c) {
; CHECK-LABEL: @threecases(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[SWITCH_TABLEIDX:%.*]] = sub i32 %c, 0
; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i32 [[SWITCH_TABLEIDX]], 3
; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i32 %c, 3
; CHECK-NEXT: br i1 [[TMP0]], label %switch.lookup, label %return
; CHECK: switch.lookup:
; CHECK-NEXT: [[SWITCH_GEP:%.*]] = getelementptr inbounds [3 x i32], [3 x i32]* @switch.table.threecases, i32 0, i32 [[SWITCH_TABLEIDX]]
; CHECK-NEXT: [[SWITCH_GEP:%.*]] = getelementptr inbounds [3 x i32], [3 x i32]* @switch.table.threecases, i32 0, i32 %c
; CHECK-NEXT: [[SWITCH_LOAD:%.*]] = load i32, i32* [[SWITCH_GEP]]
; CHECK-NEXT: ret i32 [[SWITCH_LOAD]]
; CHECK: return:
@ -1146,8 +1142,7 @@ return:
ret i32 %retval.0
; CHECK-LABEL: @reuse_cmp1(
; CHECK: entry:
; CHECK-NEXT: %switch.tableidx = sub i32 %x, 0
; CHECK-NEXT: [[C:%.+]] = icmp ult i32 %switch.tableidx, 4
; CHECK-NEXT: [[C:%.+]] = icmp ult i32 %x, 4
; CHECK-NEXT: %inverted.cmp = xor i1 [[C]], true
; CHECK: [[R:%.+]] = select i1 %inverted.cmp, i32 100, i32 {{.*}}
; CHECK-NEXT: ret i32 [[R]]

5
llvm/test/Transforms/SimplifyCFG/rangereduce.ll
View File

@ -235,11 +235,10 @@ define i8 @test7(i8 %a) optsize {
; CHECK-NEXT: [[TMP2:%.*]] = lshr i8 [[TMP1]], 2
; CHECK-NEXT: [[TMP3:%.*]] = shl i8 [[TMP1]], 6
; CHECK-NEXT: [[TMP4:%.*]] = or i8 [[TMP2]], [[TMP3]]
; CHECK-NEXT: [[SWITCH_TABLEIDX:%.*]] = sub i8 [[TMP4]], 0
; CHECK-NEXT: [[TMP5:%.*]] = icmp ult i8 [[SWITCH_TABLEIDX]], 4
; CHECK-NEXT: [[TMP5:%.*]] = icmp ult i8 [[TMP4]], 4
; CHECK-NEXT: br i1 [[TMP5]], label [[SWITCH_LOOKUP:%.*]], label [[DEF:%.*]]
; CHECK: switch.lookup:
; CHECK-NEXT: [[SWITCH_CAST:%.*]] = zext i8 [[SWITCH_TABLEIDX]] to i32
; CHECK-NEXT: [[SWITCH_CAST:%.*]] = zext i8 [[TMP4]] to i32
; CHECK-NEXT: [[SWITCH_SHIFTAMT:%.*]] = mul i32 [[SWITCH_CAST]], 8
; CHECK-NEXT: [[SWITCH_DOWNSHIFT:%.*]] = lshr i32 -943228976, [[SWITCH_SHIFTAMT]]
; CHECK-NEXT: [[SWITCH_MASKED:%.*]] = trunc i32 [[SWITCH_DOWNSHIFT]] to i8