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Revert "Canonicalize min/max expressions correctly."

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This reverts r237453 - it was causing timeouts on some bots. Reverting
while I investigate (it's probably InstCombine fighting itself...)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237458 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
James Molloy 2015-05-15 17:45:09 +00:00
parent 7363a8bcdd
commit c683eb2d37
4 changed files with 7 additions and 120 deletions
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13
lib/Transforms/InstCombine/InstCombineCompares.cpp
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@ -3970,19 +3970,6 @@ Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
}
}
// Test if the FCmpInst instruction is used exclusively by a select as
// part of a minimum or maximum operation. If so, refrain from doing
// any other folding. This helps out other analyses which understand
// non-obfuscated minimum and maximum idioms, such as ScalarEvolution
// and CodeGen. And in this case, at least one of the comparison
// operands has at least one user besides the compare (the select),
// which would often largely negate the benefit of folding anyway.
if (I.hasOneUse())
if (SelectInst *SI = dyn_cast<SelectInst>(*I.user_begin()))
if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) ||
(SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1))
return nullptr;
// Handle fcmp with constant RHS
if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
if (Instruction *LHSI = dyn_cast<Instruction>(Op0))

24
lib/Transforms/InstCombine/InstCombineSelect.cpp
View File

@ -1154,30 +1154,18 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
}
// See if we can fold the select into one of our operands.
if (SI.getType()->isIntOrIntVectorTy()) {
if (SI.getType()->isIntegerTy()) {
if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
return FoldI;
Value *LHS, *RHS, *LHS2, *RHS2;
Instruction::CastOps CastOp;
SelectPatternFlavor SPF = matchSelectPattern(&SI, LHS, RHS, &CastOp);
SelectPatternFlavor SPF = matchSelectPattern(&SI, LHS, RHS);
// MAX(MAX(a, b), a) -> MAX(a, b)
// MIN(MIN(a, b), a) -> MIN(a, b)
// MAX(MIN(a, b), a) -> a
// MIN(MAX(a, b), a) -> a
if (SPF) {
// Canonicalize so that type casts are outside select patterns.
if (LHS->getType()->getPrimitiveSizeInBits() !=
SI.getType()->getPrimitiveSizeInBits()) {
CmpInst::Predicate Pred = getICmpPredicateForMinMax(SPF);
Value *Cmp = Builder->CreateICmp(Pred, LHS, RHS);
Value *NewSI = Builder->CreateCast(CastOp,
Builder->CreateSelect(Cmp, LHS, RHS),
SI.getType());
return ReplaceInstUsesWith(SI, NewSI);
}
// MAX(MAX(a, b), a) -> MAX(a, b)
// MIN(MIN(a, b), a) -> MIN(a, b)
// MAX(MIN(a, b), a) -> a
// MIN(MAX(a, b), a) -> a
if (SelectPatternFlavor SPF2 = matchSelectPattern(LHS, LHS2, RHS2))
if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
SI, SPF, RHS))

17
lib/Transforms/InstCombine/InstructionCombining.cpp
View File

@ -714,22 +714,6 @@ Instruction *InstCombiner::FoldOpIntoSelect(Instruction &Op, SelectInst *SI) {
return nullptr;
}
// Test if a CmpInst instruction is used exclusively by a select as
// part of a minimum or maximum operation. If so, refrain from doing
// any other folding. This helps out other analyses which understand
// non-obfuscated minimum and maximum idioms, such as ScalarEvolution
// and CodeGen. And in this case, at least one of the comparison
// operands has at least one user besides the compare (the select),
// which would often largely negate the benefit of folding anyway.
if (auto *CI = dyn_cast<CmpInst>(SI->getCondition())) {
if (CI->hasOneUse()) {
Value *Op0 = CI->getOperand(0), *Op1 = CI->getOperand(1);
if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) ||
(SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1))
return nullptr;
}
}
Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, this);
Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, this);
@ -739,6 +723,7 @@ Instruction *InstCombiner::FoldOpIntoSelect(Instruction &Op, SelectInst *SI) {
return nullptr;
}
/// FoldOpIntoPhi - Given a binary operator, cast instruction, or select which
/// has a PHI node as operand #0, see if we can fold the instruction into the
/// PHI (which is only possible if all operands to the PHI are constants).

73
test/Transforms/InstCombine/minmax-fold.ll
View File

@ -1,73 +0,0 @@
; RUN: opt -S -instcombine < %s | FileCheck %s
; CHECK-LABEL: @t1
; CHECK-NEXT: icmp
; CHECK-NEXT: select
; CHECK-NEXT: sext
define i64 @t1(i32 %a) {
; This is the canonical form for a type-changing min/max.
%1 = icmp slt i32 %a, 5
%2 = select i1 %1, i32 %a, i32 5
%3 = sext i32 %2 to i64
ret i64 %3
}
; CHECK-LABEL: @t2
; CHECK-NEXT: icmp
; CHECK-NEXT: select
; CHECK-NEXT: sext
define i64 @t2(i32 %a) {
; Check this is converted into canonical form, as above.
%1 = icmp slt i32 %a, 5
%2 = sext i32 %a to i64
%3 = select i1 %1, i64 %2, i64 5
ret i64 %3
}
; CHECK-LABEL: @t3
; CHECK-NEXT: icmp
; CHECK-NEXT: select
; CHECK-NEXT: zext
define i64 @t3(i32 %a) {
; Same as @t2, with flipped operands and zext instead of sext.
%1 = icmp ult i32 %a, 5
%2 = zext i32 %a to i64
%3 = select i1 %1, i64 5, i64 %2
ret i64 %3
}
; CHECK-LABEL: @t4
; CHECK-NEXT: icmp
; CHECK-NEXT: select
; CHECK-NEXT: trunc
define i32 @t4(i64 %a) {
; Same again, with trunc.
%1 = icmp slt i64 %a, 5
%2 = trunc i64 %a to i32
%3 = select i1 %1, i32 %2, i32 5
ret i32 %3
}
; CHECK-LABEL: @t5
; CHECK-NEXT: icmp
; CHECK-NEXT: zext
; CHECK-NEXT: select
define i64 @t5(i32 %a) {
; Same as @t3, but with mismatched signedness between icmp and zext.
; InstCombine should leave this alone.
%1 = icmp slt i32 %a, 5
%2 = zext i32 %a to i64
%3 = select i1 %1, i64 5, i64 %2
ret i64 %3
}
; CHECK-LABEL: @t6
; CHECK-NEXT: icmp
; CHECK-NEXT: select
; CHECK-NEXT: sitofp
define float @t6(i32 %a) {
%1 = icmp slt i32 %a, 0
%2 = select i1 %1, i32 %a, i32 0
%3 = sitofp i32 %2 to float
ret float %3
}