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add a cl::opt override for TargetLoweringBase's JumpIsExpensive 

This patch is not intended to change existing codegen behavior for any target. 
It just exposes the JumpIsExpensive setting on the command-line to allow for
easier testing and emergency overrides.

Also, change the existing regression test to use FileCheck, explicitly specify
the jump-is-expensive option, and use more precise checks.

Differential Revision: http://reviews.llvm.org/D10846

llvm-svn: 241179
This commit is contained in:
Sanjay Patel 2015-07-01 18:10:20 +00:00
parent 0e9ff6972c
commit 943829a1ad
3 changed files with 36 additions and 17 deletions
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9
llvm/include/llvm/Target/TargetLowering.h
View File

@ -1235,11 +1235,10 @@ protected:
HasExtractBitsInsn = hasExtractInsn;
}
/// Tells the code generator not to expand sequence of operations into a
/// separate sequences that increases the amount of flow control.
void setJumpIsExpensive(bool isExpensive = true) {
JumpIsExpensive = isExpensive;
}
/// Tells the code generator not to expand logic operations on comparison
/// predicates into separate sequences that increase the amount of flow
/// control.
void setJumpIsExpensive(bool isExpensive = true);
/// Tells the code generator that integer divide is expensive, and if
/// possible, should be replaced by an alternate sequence of instructions not

13
llvm/lib/CodeGen/TargetLoweringBase.cpp
View File

@ -38,6 +38,11 @@
#include <cctype>
using namespace llvm;
static cl::opt<bool> JumpIsExpensiveOverride(
"jump-is-expensive", cl::init(false),
cl::desc("Do not create extra branches to split comparison logic."),
cl::Hidden);
/// InitLibcallNames - Set default libcall names.
///
static void InitLibcallNames(const char **Names, const Triple &TT) {
@ -757,7 +762,7 @@ TargetLoweringBase::TargetLoweringBase(const TargetMachine &tm) : TM(tm) {
IntDivIsCheap = false;
FsqrtIsCheap = false;
Pow2SDivIsCheap = false;
JumpIsExpensive = false;
JumpIsExpensive = JumpIsExpensiveOverride;
PredictableSelectIsExpensive = false;
MaskAndBranchFoldingIsLegal = false;
EnableExtLdPromotion = false;
@ -915,6 +920,12 @@ bool TargetLoweringBase::canOpTrap(unsigned Op, EVT VT) const {
}
}
void TargetLoweringBase::setJumpIsExpensive(bool isExpensive) {
// If the command-line option was specified, ignore this request.
if (!JumpIsExpensiveOverride.getNumOccurrences())
JumpIsExpensive = isExpensive;
}
TargetLoweringBase::LegalizeKind
TargetLoweringBase::getTypeConversion(LLVMContext &Context, EVT VT) const {
// If this is a simple type, use the ComputeRegisterProp mechanism.

25
llvm/test/CodeGen/X86/or-branch.ll
View File

@ -1,18 +1,27 @@
; RUN: llc < %s -march=x86 | not grep set
; RUN: llc < %s -mtriple=i386-unknown-unknown -jump-is-expensive=0 | FileCheck %s --check-prefix=JUMP2
; RUN: llc < %s -mtriple=i386-unknown-unknown -jump-is-expensive=1 | FileCheck %s --check-prefix=JUMP1
define void @foo(i32 %X, i32 %Y, i32 %Z) nounwind {
; JUMP2-LABEL: foo:
; JUMP2-DAG: jl
; JUMP2-DAG: je
;
; JUMP1-LABEL: foo:
; JUMP1-DAG: sete
; JUMP1-DAG: setl
; JUMP1: orb
; JUMP1: jne
entry:
%tmp = tail call i32 (...) @bar( ) ; <i32> [#uses=0]
%tmp.upgrd.1 = icmp eq i32 %X, 0 ; <i1> [#uses=1]
%tmp3 = icmp slt i32 %Y, 5 ; <i1> [#uses=1]
%tmp4 = or i1 %tmp3, %tmp.upgrd.1 ; <i1> [#uses=1]
%tmp1 = icmp eq i32 %X, 0
%tmp3 = icmp slt i32 %Y, 5
%tmp4 = or i1 %tmp3, %tmp1
br i1 %tmp4, label %cond_true, label %UnifiedReturnBlock
cond_true: ; preds = %entry
%tmp5 = tail call i32 (...) @bar( ) ; <i32> [#uses=0]
cond_true:
%tmp5 = tail call i32 (...) @bar( )
ret void
UnifiedReturnBlock: ; preds = %entry
UnifiedReturnBlock:
ret void
}