[llvm] r232794 - 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!
Nick Lewycky
nicholas at mxc.ca
Thu Mar 19 19:25:00 PDT 2015
Author: nicholas
Date: Thu Mar 19 21:25:00 2015
New Revision: 232794
URL: http://llvm.org/viewvc/llvm-project?rev=232794&view=rev
Log:
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!
Modified:
llvm/trunk/lib/Analysis/ScalarEvolution.cpp
llvm/trunk/test/Analysis/ScalarEvolution/fold.ll
Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=232794&r1=232793&r2=232794&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Thu Mar 19 21:25:00 2015
@@ -1102,13 +1102,14 @@ const SCEV *ScalarEvolution::getTruncate
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::getTruncate
}
// 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)
Modified: llvm/trunk/test/Analysis/ScalarEvolution/fold.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/ScalarEvolution/fold.ll?rev=232794&r1=232793&r2=232794&view=diff
==============================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/fold.ll (original)
+++ llvm/trunk/test/Analysis/ScalarEvolution/fold.ll Thu Mar 19 21:25:00 2015
@@ -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
+}
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