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When simplifying a SCEV truncate by distributing, consider it a simplification to replace a cast, even if we end up with a trunc around the term. Fixes PR22960!

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232794 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2015-03-20 02:25:00 +00:00
parent 67934e4b41
commit bea9b06e84
2 changed files with 18 additions and 4 deletions
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10
lib/Analysis/ScalarEvolution.cpp
View File

@ -1102,13 +1102,14 @@ const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
return getTruncateOrZeroExtend(SZ->getOperand(), Ty);
// trunc(x1+x2+...+xN) --> trunc(x1)+trunc(x2)+...+trunc(xN) if we can
// eliminate all the truncates.
// eliminate all the truncates, or we replace extensions with truncates.
if (const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Op)) {
SmallVector<const SCEV *, 4> Operands;
bool hasTrunc = false;
for (unsigned i = 0, e = SA->getNumOperands(); i != e && !hasTrunc; ++i) {
const SCEV *S = getTruncateExpr(SA->getOperand(i), Ty);
hasTrunc = isa<SCEVTruncateExpr>(S);
if (!isa<SCEVCastExpr>(SA->getOperand(i)))
hasTrunc = isa<SCEVTruncateExpr>(S);
Operands.push_back(S);
}
if (!hasTrunc)
@ -1117,13 +1118,14 @@ const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
}
// trunc(x1*x2*...*xN) --> trunc(x1)*trunc(x2)*...*trunc(xN) if we can
// eliminate all the truncates.
// eliminate all the truncates, or we replace other casts with truncates.
if (const SCEVMulExpr *SM = dyn_cast<SCEVMulExpr>(Op)) {
SmallVector<const SCEV *, 4> Operands;
bool hasTrunc = false;
for (unsigned i = 0, e = SM->getNumOperands(); i != e && !hasTrunc; ++i) {
const SCEV *S = getTruncateExpr(SM->getOperand(i), Ty);
hasTrunc = isa<SCEVTruncateExpr>(S);
if (!isa<SCEVCastExpr>(SM->getOperand(i)))
hasTrunc = isa<SCEVTruncateExpr>(S);
Operands.push_back(S);
}
if (!hasTrunc)

12
test/Analysis/ScalarEvolution/fold.ll
View File

@ -86,3 +86,15 @@ define void @test6(i8 %x) {
; CHECK: --> (2048 * ((zext i8 %x to i16) /u 8))
ret void
}
; PR22960
define void @test7(i32 %A) {
; CHECK-LABEL: @test7
%B = sext i32 %A to i64
%C = zext i32 %A to i64
%D = sub i64 %B, %C
%E = trunc i64 %D to i16
; CHECK: %E
; CHECK-NEXT: --> 0
ret void
}