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Switch the select to branch transformation on by default.

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The primitive conservative heuristic seems to give a slight overall
improvement while not regressing stuff. Make it available to wider
testing. If you notice any speed regressions (or significant code
size regressions) let me know!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156258 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer
2012-05-06 14:25:16 +00:00
parent 58c1da84f2
commit 77c4ef8a47
3 changed files with 6 additions and 5 deletions
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7
lib/Transforms/Scalar/CodeGenPrepare.cpp
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@@ -71,8 +71,9 @@ static cl::opt<bool> DisableDeleteDeadBlocks(
"disable-cgp-delete-dead-blocks", cl::Hidden, cl::init(false), "disable-cgp-delete-dead-blocks", cl::Hidden, cl::init(false),
cl::desc("Disable deleting dead blocks in CodeGenPrepare")); cl::desc("Disable deleting dead blocks in CodeGenPrepare"));
static cl::opt<bool> EnableSelectToBranch("enable-cgp-select2branch", cl::Hidden, static cl::opt<bool> DisableSelectToBranch(
cl::desc("Enable select to branch conversion.")); "disable-cgp-select2branch", cl::Hidden, cl::init(false),
cl::desc("Disable select to branch conversion."));
namespace { namespace {
class CodeGenPrepare : public FunctionPass { class CodeGenPrepare : public FunctionPass {
@@ -1132,7 +1133,7 @@ static bool isFormingBranchFromSelectProfitable(SelectInst *SI) {
bool CodeGenPrepare::OptimizeSelectInst(SelectInst *SI) { bool CodeGenPrepare::OptimizeSelectInst(SelectInst *SI) {
// If we have a SelectInst that will likely profit from branch prediction, // If we have a SelectInst that will likely profit from branch prediction,
// turn it into a branch. // turn it into a branch.
if (!EnableSelectToBranch || OptSize || !TLI->isPredictableSelectExpensive()) if (DisableSelectToBranch || OptSize || !TLI->isPredictableSelectExpensive())
return false; return false;
if (!SI->getCondition()->getType()->isIntegerTy(1) || if (!SI->getCondition()->getType()->isIntegerTy(1) ||

2
test/CodeGen/X86/cmov-into-branch.ll
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@@ -1,4 +1,4 @@
; RUN: llc -march=x86-64 -mcpu=core2 -enable-cgp-select2branch < %s | FileCheck %s ; RUN: llc -march=x86-64 -mcpu=core2 < %s | FileCheck %s
; cmp with single-use load, should not form cmov. ; cmp with single-use load, should not form cmov.
define i32 @test1(double %a, double* nocapture %b, i32 %x, i32 %y) { define i32 @test1(double %a, double* nocapture %b, i32 %x, i32 %y) {

2
test/CodeGen/X86/cmov.ll
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@@ -1,4 +1,4 @@
; RUN: llc < %s -mtriple=x86_64-apple-darwin10 | FileCheck %s ; RUN: llc < %s -mtriple=x86_64-apple-darwin10 -disable-cgp-select2branch | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128" target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
define i32 @test1(i32 %x, i32 %n, i32 %w, i32* %vp) nounwind readnone { define i32 @test1(i32 %x, i32 %n, i32 %w, i32* %vp) nounwind readnone {