[llvm] r367485 - [IndVars, RLEV] Support rewriting exit values in loops without known exits (prep work)
Philip Reames via llvm-commits
llvm-commits at lists.llvm.org
Wed Jul 31 14:15:21 PDT 2019
Author: reames
Date: Wed Jul 31 14:15:21 2019
New Revision: 367485
URL: http://llvm.org/viewvc/llvm-project?rev=367485&view=rev
Log:
[IndVars, RLEV] Support rewriting exit values in loops without known exits (prep work)
This is a prepatory patch for future work on support exit value rewriting in loops with a mixture of computable and non-computable exit counts. The intention is to be "mostly NFC" - i.e. not enable any interesting new transforms - but in practice, there are some small output changes.
The test differences are caused by cases wherewhere getSCEVAtScope can simplify a single entry phi without needing any knowledge of the loop.
Modified:
llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
llvm/trunk/test/Transforms/IndVarSimplify/lftr-pr20680.ll
llvm/trunk/test/Transforms/IndVarSimplify/pr38674.ll
Modified: llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp?rev=367485&r1=367484&r2=367485&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp Wed Jul 31 14:15:21 2019
@@ -630,7 +630,8 @@ bool IndVarSimplify::rewriteLoopExitValu
// and varies predictably *inside* the loop. Evaluate the value it
// contains when the loop exits, if possible.
const SCEV *ExitValue = SE->getSCEVAtScope(Inst, L->getParentLoop());
- if (!SE->isLoopInvariant(ExitValue, L) ||
+ if (isa<SCEVCouldNotCompute>(ExitValue) ||
+ !SE->isLoopInvariant(ExitValue, L) ||
!isSafeToExpand(ExitValue, *SE))
continue;
@@ -804,7 +805,7 @@ bool IndVarSimplify::canLoopBeDeleted(
L->getExitingBlocks(ExitingBlocks);
SmallVector<BasicBlock *, 8> ExitBlocks;
L->getUniqueExitBlocks(ExitBlocks);
- if (ExitBlocks.size() > 1 || ExitingBlocks.size() > 1)
+ if (ExitBlocks.size() != 1 || ExitingBlocks.size() != 1)
return false;
BasicBlock *ExitBlock = ExitBlocks[0];
@@ -2774,14 +2775,11 @@ bool IndVarSimplify::run(Loop *L) {
Rewriter.disableCanonicalMode();
Changed |= simplifyAndExtend(L, Rewriter, LI);
- // Check to see if this loop has a computable loop-invariant execution count.
- // If so, this means that we can compute the final value of any expressions
+ // Check to see if we can compute the final value of any expressions
// that are recurrent in the loop, and substitute the exit values from the
- // loop into any instructions outside of the loop that use the final values of
- // the current expressions.
- //
- if (ReplaceExitValue != NeverRepl &&
- !isa<SCEVCouldNotCompute>(BackedgeTakenCount))
+ // loop into any instructions outside of the loop that use the final values
+ // of the current expressions.
+ if (ReplaceExitValue != NeverRepl)
Changed |= rewriteLoopExitValues(L, Rewriter);
// Eliminate redundant IV cycles.
Modified: llvm/trunk/test/Transforms/IndVarSimplify/lftr-pr20680.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/lftr-pr20680.ll?rev=367485&r1=367484&r2=367485&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/lftr-pr20680.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/lftr-pr20680.ll Wed Jul 31 14:15:21 2019
@@ -62,7 +62,6 @@ define void @f() {
; CHECK: cond.false.us:
; CHECK-NEXT: br label [[COND_END_US]]
; CHECK: cond.end.us:
-; CHECK-NEXT: [[COND_US:%.*]] = phi i32 [ [[DIV]], [[COND_FALSE_US]] ], [ [[INDVARS_IV]], [[FOR_BODY3_US]] ]
; CHECK-NEXT: [[TMP6:%.*]] = load i32, i32* @b, align 4
; CHECK-NEXT: [[CMP91_US:%.*]] = icmp slt i32 [[TMP6]], 1
; CHECK-NEXT: br i1 [[CMP91_US]], label [[FOR_INC_LR_PH_US:%.*]], label [[FOR_COND2_LOOPEXIT_US:%.*]]
@@ -79,10 +78,9 @@ define void @f() {
; CHECK-NEXT: store i32 1, i32* @b, align 4
; CHECK-NEXT: br label [[FOR_COND2_LOOPEXIT_US]]
; CHECK: for.cond2.for.inc13_crit_edge.us-lcssa.us.us-lcssa:
-; CHECK-NEXT: [[COND_LCSSA_PH_US_PH:%.*]] = phi i32 [ [[COND_US]], [[FOR_COND2_LOOPEXIT_US]] ]
; CHECK-NEXT: br label [[FOR_COND2_FOR_INC13_CRIT_EDGE_US_LCSSA_US]]
; CHECK: for.cond2.for.inc13_crit_edge.us-lcssa.us:
-; CHECK-NEXT: [[COND_LCSSA_PH_US:%.*]] = phi i32 [ [[COND_LCSSA_PH_US_PH]], [[FOR_COND2_FOR_INC13_CRIT_EDGE_US_LCSSA_US_US_LCSSA]] ], [ [[DIV]], [[FOR_COND2_FOR_INC13_CRIT_EDGE_US_LCSSA_US_US_LCSSA_US]] ]
+; CHECK-NEXT: [[COND_LCSSA_PH_US:%.*]] = phi i32 [ [[DIV]], [[FOR_COND2_FOR_INC13_CRIT_EDGE_US_LCSSA_US_US_LCSSA]] ], [ [[DIV]], [[FOR_COND2_FOR_INC13_CRIT_EDGE_US_LCSSA_US_US_LCSSA_US]] ]
; CHECK-NEXT: br label [[FOR_COND2_FOR_INC13_CRIT_EDGE:%.*]]
; CHECK: for.body3.lr.ph.split:
; CHECK-NEXT: br i1 [[TOBOOL]], label [[FOR_BODY3_LR_PH_SPLIT_SPLIT_US:%.*]], label [[FOR_BODY3_LR_PH_SPLIT_FOR_BODY3_LR_PH_SPLIT_SPLIT_CRIT_EDGE:%.*]]
Modified: llvm/trunk/test/Transforms/IndVarSimplify/pr38674.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/pr38674.ll?rev=367485&r1=367484&r2=367485&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/pr38674.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/pr38674.ll Wed Jul 31 14:15:21 2019
@@ -92,15 +92,13 @@ define i32 @test_02(i32 %x) {
; CHECK: for.end:
; CHECK-NEXT: br i1 false, label [[FOR_COND4_PREHEADER]], label [[FOR_END9:%.*]]
; CHECK: for.end9:
-; CHECK-NEXT: [[INC11:%.*]] = add nuw nsw i32 0, [[X]]
; CHECK-NEXT: br i1 false, label [[FOR_COND1_PREHEADER]], label [[RETURN_LOOPEXIT3:%.*]]
; CHECK: return.loopexit:
; CHECK-NEXT: unreachable
; CHECK: return.loopexit3:
-; CHECK-NEXT: [[INC11_LCSSA:%.*]] = phi i32 [ [[INC11]], [[FOR_END9]] ]
; CHECK-NEXT: br label [[RETURN:%.*]]
; CHECK: return:
-; CHECK-NEXT: ret i32 [[INC11_LCSSA]]
+; CHECK-NEXT: ret i32 [[X]]
;
entry:
br label %for.cond1.preheader
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