[llvm] r230921 - Revert some changes that were made to fix PR20680.
Sanjoy Das
sanjoy at playingwithpointers.com
Sun Mar 1 15:36:27 PST 2015
Author: sanjoy
Date: Sun Mar 1 17:36:26 2015
New Revision: 230921
URL: http://llvm.org/viewvc/llvm-project?rev=230921&view=rev
Log:
Revert some changes that were made to fix PR20680.
Summary:
As far as I can tell, the real bug causing the issue was fixed in
r230533. SCEVExpander should mark an increment operation as nuw or nsw
only if it can *prove* that the operation does not overflow. There
shouldn't be any situation where we have to do something different
because of no-wrap flags generated by SCEVExpander.
Revert "IndVarSimplify: Allow LFTR to fire more often"
This reverts commit 1ade0f0faa98877b688e0b9da58e876052c1e04e (SVN: 222213).
Revert "IndVarSimplify: Don't let LFTR compare against a poison value"
This reverts commit c0f2b8b528d8a37b0a1522aae90af649d6357eb5 (SVN: 217102).
Reviewers: majnemer, atrick, spatel
Differential Revision: http://reviews.llvm.org/D7979
Modified:
llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
llvm/trunk/test/Transforms/IndVarSimplify/2011-10-27-lftrnull.ll
llvm/trunk/test/Transforms/IndVarSimplify/lftr-address-space-pointers.ll
llvm/trunk/test/Transforms/IndVarSimplify/lftr-reuse.ll
Modified: llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp?rev=230921&r1=230920&r2=230921&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp Sun Mar 1 17:36:26 2015
@@ -1705,51 +1705,15 @@ LinearFunctionTestReplace(Loop *L,
// compare against the post-incremented value, otherwise we must compare
// against the preincremented value.
if (L->getExitingBlock() == L->getLoopLatch()) {
+ // Add one to the "backedge-taken" count to get the trip count.
+ // This addition may overflow, which is valid as long as the comparison is
+ // truncated to BackedgeTakenCount->getType().
+ IVCount = SE->getAddExpr(BackedgeTakenCount,
+ SE->getConstant(BackedgeTakenCount->getType(), 1));
// The BackedgeTaken expression contains the number of times that the
// backedge branches to the loop header. This is one less than the
// number of times the loop executes, so use the incremented indvar.
- llvm::Value *IncrementedIndvar =
- IndVar->getIncomingValueForBlock(L->getExitingBlock());
- const auto *IncrementedIndvarSCEV =
- cast<SCEVAddRecExpr>(SE->getSCEV(IncrementedIndvar));
- // It is unsafe to use the incremented indvar if it has a wrapping flag, we
- // don't want to compare against a poison value. Check the SCEV that
- // corresponds to the incremented indvar, the SCEVExpander will only insert
- // flags in the IR if the SCEV originally had wrapping flags.
- // FIXME: In theory, SCEV could drop flags even though they exist in IR.
- // A more robust solution would involve getting a new expression for
- // CmpIndVar by applying non-NSW/NUW AddExprs.
- auto WrappingFlags =
- ScalarEvolution::setFlags(SCEV::FlagNUW, SCEV::FlagNSW);
- const SCEV *IVInit = IncrementedIndvarSCEV->getStart();
- if (SE->getTypeSizeInBits(IVInit->getType()) >
- SE->getTypeSizeInBits(IVCount->getType()))
- IVInit = SE->getTruncateExpr(IVInit, IVCount->getType());
- unsigned BitWidth = SE->getTypeSizeInBits(IVCount->getType());
- Type *WideTy = IntegerType::get(SE->getContext(), BitWidth + 1);
- // Check if InitIV + BECount+1 requires sign/zero extension.
- // If not, clear the corresponding flag from WrappingFlags because it is not
- // necessary for those flags in the IncrementedIndvarSCEV expression.
- if (SE->getSignExtendExpr(SE->getAddExpr(IVInit, BackedgeTakenCount),
- WideTy) ==
- SE->getAddExpr(SE->getSignExtendExpr(IVInit, WideTy),
- SE->getSignExtendExpr(BackedgeTakenCount, WideTy)))
- WrappingFlags = ScalarEvolution::clearFlags(WrappingFlags, SCEV::FlagNSW);
- if (SE->getZeroExtendExpr(SE->getAddExpr(IVInit, BackedgeTakenCount),
- WideTy) ==
- SE->getAddExpr(SE->getZeroExtendExpr(IVInit, WideTy),
- SE->getZeroExtendExpr(BackedgeTakenCount, WideTy)))
- WrappingFlags = ScalarEvolution::clearFlags(WrappingFlags, SCEV::FlagNUW);
- if (!ScalarEvolution::maskFlags(IncrementedIndvarSCEV->getNoWrapFlags(),
- WrappingFlags)) {
- // Add one to the "backedge-taken" count to get the trip count.
- // This addition may overflow, which is valid as long as the comparison is
- // truncated to BackedgeTakenCount->getType().
- IVCount =
- SE->getAddExpr(BackedgeTakenCount,
- SE->getConstant(BackedgeTakenCount->getType(), 1));
- CmpIndVar = IncrementedIndvar;
- }
+ CmpIndVar = IndVar->getIncomingValueForBlock(L->getExitingBlock());
}
Value *ExitCnt = genLoopLimit(IndVar, IVCount, L, Rewriter, SE);
Modified: llvm/trunk/test/Transforms/IndVarSimplify/2011-10-27-lftrnull.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/2011-10-27-lftrnull.ll?rev=230921&r1=230920&r2=230921&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/2011-10-27-lftrnull.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/2011-10-27-lftrnull.ll Sun Mar 1 17:36:26 2015
@@ -6,7 +6,7 @@ target triple = "thumbv7-apple-darwin"
; CHECK-LABEL: @test(
; CHECK: if.end.i126:
-; CHECK: %exitcond = icmp ne i8* %destYPixelPtr.010.i, getelementptr (i8* null, i32 undef)
+; CHECK: %exitcond = icmp ne i8* %incdec.ptr.i, getelementptr (i8* null, i32 undef)
define void @test() nounwind {
entry:
br label %while.cond
Modified: llvm/trunk/test/Transforms/IndVarSimplify/lftr-address-space-pointers.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/lftr-address-space-pointers.ll?rev=230921&r1=230920&r2=230921&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/lftr-address-space-pointers.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/lftr-address-space-pointers.ll Sun Mar 1 17:36:26 2015
@@ -11,7 +11,7 @@ entry:
br i1 %cmp1, label %for.body, label %for.end
; Make sure the added GEP has the right index type
-; CHECK: %lftr.limit = getelementptr i8, i8 addrspace(2)* %base, i8
+; CHECK: %lftr.limit = getelementptr i8, i8 addrspace(2)* %base, i8 %0
; CHECK: for.body:
; CHECK: phi i8 addrspace(2)*
@@ -43,7 +43,7 @@ entry:
br i1 %cmp1, label %for.body, label %for.end
; Make sure the added GEP has the right index type
-; CHECK: %lftr.limit = getelementptr i8, i8 addrspace(3)* %base, i16
+; CHECK: %lftr.limit = getelementptr i8, i8 addrspace(3)* %base, i16 %0
; CHECK: for.body:
; CHECK: phi i8 addrspace(3)*
Modified: llvm/trunk/test/Transforms/IndVarSimplify/lftr-reuse.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/lftr-reuse.ll?rev=230921&r1=230920&r2=230921&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/lftr-reuse.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/lftr-reuse.ll Sun Mar 1 17:36:26 2015
@@ -82,23 +82,15 @@ exit:
; Perform LFTR without generating extra preheader code.
define void @guardedloop([0 x double]* %matrix, [0 x double]* %vector,
i32 %irow, i32 %ilead) nounwind {
-; CHECK-LABEL: @guardedloop(
-; CHECK-LABEL: entry:
-; CHECK-NEXT: %[[cmp:.*]] = icmp slt i32 1, %irow
-; CHECK-NEXT: br i1 %[[cmp]], label %[[loop_preheader:.*]], label %[[return:.*]]
-
-; CHECK: [[loop_preheader]]:
-; CHECK-NEXT: %[[sext:.*]] = sext i32 %ilead to i64
-; CHECK-NEXT: %[[add:.*]] = add i32 %irow, -1
-; CHECK-NEXT: br label %[[loop:.*]]
-
-; CHECK: [[loop]]:
-; CHECK-NEXT: %[[indvars_iv2:.*]] = phi i64
-; CHECK-NEXT: phi i64
+; CHECK: entry:
+; CHECK-NOT: zext
+; CHECK-NOT: add
+; CHECK: loop:
+; CHECK: phi i64
+; CHECK: phi i64
; CHECK-NOT: phi
-; CHECK: %[[lftr_wideiv:.*]] = trunc i64 %[[indvars_iv2]] to i32
-; CHECK-NEXT: %[[exitcond:.*]] = icmp ne i32 %[[lftr_wideiv]], %[[add]]
-; CHECK-NEXT: br i1 %[[exitcond]], label %[[loop]], label
+; CHECK: icmp ne
+; CHECK: br i1
entry:
%cmp = icmp slt i32 1, %irow
br i1 %cmp, label %loop, label %return
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