[llvm] dc81e69 - [IndVars] Check expansion safety in makeIVComparisonInvariant() (PR62992)
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Wed May 31 02:21:43 PDT 2023
Author: Nikita Popov
Date: 2023-05-31T11:21:35+02:00
New Revision: dc81e69eb126ea1dbab202733ae34b1a3d6eb0cf
URL: https://github.com/llvm/llvm-project/commit/dc81e69eb126ea1dbab202733ae34b1a3d6eb0cf
DIFF: https://github.com/llvm/llvm-project/commit/dc81e69eb126ea1dbab202733ae34b1a3d6eb0cf.diff
LOG: [IndVars] Check expansion safety in makeIVComparisonInvariant() (PR62992)
Make sure the invariant expressions are safe to expand. In
particular, we should not speculative a trapping division into
the preheader.
Fixes https://github.com/llvm/llvm-project/issues/62992.
Added:
llvm/test/Transforms/IndVarSimplify/pr62992.ll
Modified:
llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
index 1458e6184861c..62821f149f444 100644
--- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -217,8 +217,10 @@ bool SimplifyIndvar::makeIVComparisonInvariant(ICmpInst *ICmp,
// Do not generate something ridiculous.
auto *PHTerm = Preheader->getTerminator();
- if (Rewriter.isHighCostExpansion({ InvariantLHS, InvariantRHS }, L,
- 2 * SCEVCheapExpansionBudget, TTI, PHTerm))
+ if (Rewriter.isHighCostExpansion({InvariantLHS, InvariantRHS}, L,
+ 2 * SCEVCheapExpansionBudget, TTI, PHTerm) ||
+ !Rewriter.isSafeToExpandAt(InvariantLHS, PHTerm) ||
+ !Rewriter.isSafeToExpandAt(InvariantRHS, PHTerm))
return false;
auto *NewLHS =
Rewriter.expandCodeFor(InvariantLHS, IVOperand->getType(), PHTerm);
diff --git a/llvm/test/Transforms/IndVarSimplify/pr62992.ll b/llvm/test/Transforms/IndVarSimplify/pr62992.ll
new file mode 100644
index 0000000000000..c8f47b57f1eda
--- /dev/null
+++ b/llvm/test/Transforms/IndVarSimplify/pr62992.ll
@@ -0,0 +1,46 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
+; RUN: opt -S -passes=indvars < %s | FileCheck %s
+
+declare void @use(i1)
+
+; Make sure the division does not get expanded into the preheader.
+
+define i32 @test(i32 %arg) {
+; CHECK-LABEL: define i32 @test
+; CHECK-SAME: (i32 [[ARG:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br label [[LOOP:%.*]]
+; CHECK: loop:
+; CHECK-NEXT: br i1 false, label [[IF:%.*]], label [[LOOP_LATCH:%.*]]
+; CHECK: if:
+; CHECK-NEXT: [[DIV:%.*]] = udiv i32 7, [[ARG]]
+; CHECK-NEXT: [[CMP2:%.*]] = icmp ult i32 1, [[DIV]]
+; CHECK-NEXT: call void @use(i1 [[CMP2]])
+; CHECK-NEXT: br label [[LOOP_LATCH]]
+; CHECK: loop.latch:
+; CHECK-NEXT: br i1 false, label [[LOOP]], label [[EXIT:%.*]]
+; CHECK: exit:
+; CHECK-NEXT: ret i32 1
+;
+entry:
+ br label %loop
+
+loop:
+ %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop.latch ]
+ %iv.next = add i32 %iv, 1
+ %cmp = icmp eq i32 %iv, 1
+ br i1 %cmp, label %if, label %loop.latch
+
+if:
+ %div = udiv i32 7, %arg
+ %cmp2 = icmp ult i32 %iv.next, %div
+ call void @use(i1 %cmp2)
+ br label %loop.latch
+
+loop.latch:
+ br i1 false, label %loop, label %exit
+
+exit:
+ %inc.lcssa = phi i32 [ %iv.next, %loop.latch ]
+ ret i32 %inc.lcssa
+}
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