[llvm] r246691 - use "unpredictable" metadata in SelectionDAG when splitting compares
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Wed Sep 2 12:17:25 PDT 2015
Author: spatel
Date: Wed Sep 2 14:17:25 2015
New Revision: 246691
URL: http://llvm.org/viewvc/llvm-project?rev=246691&view=rev
Log:
use "unpredictable" metadata in SelectionDAG when splitting compares
This patch uses the metadata defined in D12341 to avoid creating an unpredictable branch.
Differential Revision: http://reviews.llvm.org/D12343
Modified:
llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
llvm/trunk/test/CodeGen/X86/or-branch.ll
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp?rev=246691&r1=246690&r2=246691&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp Wed Sep 2 14:17:25 2015
@@ -1625,11 +1625,12 @@ void SelectionDAGBuilder::visitBr(const
// jle foo
//
if (const BinaryOperator *BOp = dyn_cast<BinaryOperator>(CondVal)) {
- if (!DAG.getTargetLoweringInfo().isJumpExpensive() &&
- BOp->hasOneUse() && (BOp->getOpcode() == Instruction::And ||
- BOp->getOpcode() == Instruction::Or)) {
+ Instruction::BinaryOps Opcode = BOp->getOpcode();
+ if (!DAG.getTargetLoweringInfo().isJumpExpensive() && BOp->hasOneUse() &&
+ !I.getMetadata(LLVMContext::MD_unpredictable) &&
+ (Opcode == Instruction::And || Opcode == Instruction::Or)) {
FindMergedConditions(BOp, Succ0MBB, Succ1MBB, BrMBB, BrMBB,
- BOp->getOpcode(), getEdgeWeight(BrMBB, Succ0MBB),
+ Opcode, getEdgeWeight(BrMBB, Succ0MBB),
getEdgeWeight(BrMBB, Succ1MBB));
// If the compares in later blocks need to use values not currently
// exported from this block, export them now. This block should always
Modified: llvm/trunk/test/CodeGen/X86/or-branch.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/or-branch.ll?rev=246691&r1=246690&r2=246691&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/or-branch.ll (original)
+++ llvm/trunk/test/CodeGen/X86/or-branch.ll Wed Sep 2 14:17:25 2015
@@ -1,5 +1,5 @@
-; 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
+; RUN: llc < %s -mtriple=i386-unknown-unknown -jump-is-expensive=0 | FileCheck %s --check-prefix=JUMP2 --check-prefix=CHECK
+; RUN: llc < %s -mtriple=i386-unknown-unknown -jump-is-expensive=1 | FileCheck %s --check-prefix=JUMP1 --check-prefix=CHECK
define void @foo(i32 %X, i32 %Y, i32 %Z) nounwind {
; JUMP2-LABEL: foo:
@@ -25,4 +25,30 @@ UnifiedReturnBlock:
ret void
}
+; If the branch is unpredictable, don't add another branch
+; regardless of whether they are expensive or not.
+
+define void @unpredictable(i32 %X, i32 %Y, i32 %Z) nounwind {
+; CHECK-LABEL: unpredictable:
+; CHECK-DAG: sete
+; CHECK-DAG: setl
+; CHECK: orb
+; CHECK: jne
+entry:
+ %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, !unpredictable !0
+
+cond_true:
+ %tmp5 = tail call i32 (...) @bar( )
+ ret void
+
+UnifiedReturnBlock:
+ ret void
+}
+
declare i32 @bar(...)
+
+!0 = !{}
+
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