[llvm] r211730 - [FastISel][X86] Only fold the cmp into the select when both instructions are in the same basic block.
Juergen Ributzka
juergen at apple.com
Wed Jun 25 13:06:12 PDT 2014
Author: ributzka
Date: Wed Jun 25 15:06:12 2014
New Revision: 211730
URL: http://llvm.org/viewvc/llvm-project?rev=211730&view=rev
Log:
[FastISel][X86] Only fold the cmp into the select when both instructions are in the same basic block.
If the cmp is in a different basic block, then it is possible that not all
operands of that compare have defined registers. This can happen when one of
the operands to the cmp is a load and the load gets folded into the cmp. In
this case FastISel will skip the load instruction and the vreg is never
defined.
Added:
llvm/trunk/test/CodeGen/X86/fast-isel-select-cmp.ll
Modified:
llvm/trunk/lib/Target/X86/X86FastISel.cpp
Modified: llvm/trunk/lib/Target/X86/X86FastISel.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86FastISel.cpp?rev=211730&r1=211729&r2=211730&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86FastISel.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86FastISel.cpp Wed Jun 25 15:06:12 2014
@@ -1754,8 +1754,11 @@ bool X86FastISel::X86FastEmitCMoveSelect
const TargetRegisterClass *RC = TLI.getRegClassFor(RetVT);
bool NeedTest = true;
- // Optimize conditons coming from a compare.
- if (const auto *CI = dyn_cast<CmpInst>(Cond)) {
+ // Optimize conditons coming from a compare if both instructions are in the
+ // same basic block (values defined in other basic blocks may not have
+ // initialized registers).
+ const auto *CI = dyn_cast<CmpInst>(Cond);
+ if (CI && (CI->getParent() == I->getParent())) {
CmpInst::Predicate Predicate = optimizeCmpPredicate(CI);
// FCMP_OEQ and FCMP_UNE cannot be checked with a single instruction.
@@ -1927,8 +1930,11 @@ bool X86FastISel::X86FastEmitSSESelect(c
if (!isTypeLegal(I->getType(), RetVT))
return false;
+ // Optimize conditons coming from a compare if both instructions are in the
+ // same basic block (values defined in other basic blocks may not have
+ // initialized registers).
const auto *CI = dyn_cast<FCmpInst>(I->getOperand(0));
- if (!CI)
+ if (!CI || (CI->getParent() != I->getParent()))
return false;
if (I->getType() != CI->getOperand(0)->getType() ||
@@ -2023,8 +2029,12 @@ bool X86FastISel::X86FastEmitPseudoSelec
const Value *Cond = I->getOperand(0);
X86::CondCode CC = X86::COND_NE;
- // Don't emit a test if the condition comes from a compare.
- if (const auto *CI = dyn_cast<CmpInst>(Cond)) {
+
+ // Optimize conditons coming from a compare if both instructions are in the
+ // same basic block (values defined in other basic blocks may not have
+ // initialized registers).
+ const auto *CI = dyn_cast<CmpInst>(Cond);
+ if (CI && (CI->getParent() == I->getParent())) {
bool NeedSwap;
std::tie(CC, NeedSwap) = getX86ConditonCode(CI->getPredicate());
if (CC > X86::LAST_VALID_COND)
Added: llvm/trunk/test/CodeGen/X86/fast-isel-select-cmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/fast-isel-select-cmp.ll?rev=211730&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/fast-isel-select-cmp.ll (added)
+++ llvm/trunk/test/CodeGen/X86/fast-isel-select-cmp.ll Wed Jun 25 15:06:12 2014
@@ -0,0 +1,50 @@
+; RUN: llc < %s -O0 -mtriple=x86_64-apple-darwin10 | FileCheck %s
+
+; Test if we do not fold the cmp into select if the instructions are in
+; different basic blocks.
+
+define i32 @select_cmp_cmov_i32(i32 %a, i32 %b) {
+; CHECK-LABEL: select_cmp_cmov_i32
+; CHECK-LABEL: continue
+; CHECK-NOT: cmp
+ %1 = icmp ult i32 %a, %b
+ br i1 %1, label %continue, label %exit
+
+continue:
+ %2 = select i1 %1, i32 %a, i32 %b
+ ret i32 %2
+
+exit:
+ ret i32 -1
+}
+
+define float @select_fcmp_oeq_f32(float %a, float %b, float %c, float %d) {
+; CHECK-LABEL: select_fcmp_oeq_f32
+; CHECK-LABEL: continue
+; CHECK-NOT: cmp
+ %1 = fcmp oeq float %a, %b
+ br i1 %1, label %continue, label %exit
+
+continue:
+ %2 = select i1 %1, float %c, float %d
+ ret float %2
+
+exit:
+ ret float -1.0
+}
+
+define float @select_fcmp_one_f32(float %a, float %b, float %c, float %d) {
+; CHECK-LABEL: select_fcmp_one_f32
+; CHECK-LABEL: continue
+; CHECK-NOT: ucomi
+ %1 = fcmp one float %a, %b
+ br i1 %1, label %continue, label %exit
+
+continue:
+ %2 = select i1 %1, float %c, float %d
+ ret float %2
+
+exit:
+ ret float -1.0
+}
+
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