[PATCH] D145677: [ConstraintElimination] Fix undefined behaviour in shl decomposition

[Zain Jaffal via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG7faa8c6ec6d4: [ConstraintElimination] Fix undefined behaviour in shl decomposition (authored by zjaffal).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D145677/new/

https://reviews.llvm.org/D145677

Files:
  llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
  llvm/test/Transforms/ConstraintElimination/shl.ll


Index: llvm/test/Transforms/ConstraintElimination/shl.ll
===================================================================
--- llvm/test/Transforms/ConstraintElimination/shl.ll
+++ llvm/test/Transforms/ConstraintElimination/shl.ll
@@ -1223,3 +1223,55 @@
   %f.1 = icmp ule i8 %start.add.2.13, %start.shl.4
   ret i1 %f.1
 }
+
+define i1 @shl_overflow(i64 %start) {
+; CHECK-LABEL: @shl_overflow(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[PRE_COND:%.*]] = icmp ugt i64 [[START:%.*]], 0
+; CHECK-NEXT:    br i1 [[PRE_COND]], label [[MAIN:%.*]], label [[EXIT:%.*]]
+; CHECK:       main:
+; CHECK-NEXT:    [[TMP0:%.*]] = shl nuw nsw i64 [[START]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp uge i64 [[TMP0]], [[START]]
+; CHECK-NEXT:    ret i1 [[TMP1]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret i1 false
+;
+entry:
+  %pre.cond = icmp ugt i64 %start, 0
+  br i1 %pre.cond, label %main, label %exit
+
+main:
+  %0 = shl nuw nsw i64 %start, -1
+  %1 = icmp uge i64 %0, %start
+  ret i1 %1
+
+exit:
+  ret i1 0
+}
+
+
+define i1 @shl_overflow_2() {
+; CHECK-LABEL: @shl_overflow_2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[SHL_UB:%.*]] = shl nuw nsw i256 0, 64
+; CHECK-NEXT:    [[SHL_CMP:%.*]] = icmp uge i256 [[SHL_UB]], 0
+; CHECK-NEXT:    ret i1 [[SHL_CMP]]
+;
+entry:
+  %shl.ub = shl nuw nsw i256 0, 64
+  %shl.cmp = icmp uge i256 %shl.ub, 0
+  ret i1 %shl.cmp
+}
+
+define i1 @shl_overflow_3() {
+; CHECK-LABEL: @shl_overflow_3(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[SHL_UB:%.*]] = shl nuw nsw i256 0, 65
+; CHECK-NEXT:    [[SHL_CMP:%.*]] = icmp uge i256 [[SHL_UB]], 0
+; CHECK-NEXT:    ret i1 [[SHL_CMP]]
+;
+entry:
+  %shl.ub = shl nuw nsw i256 0, 65
+  %shl.cmp = icmp uge i256 %shl.ub, 0
+  ret i1 %shl.cmp
+}
Index: llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
+++ llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
@@ -377,7 +377,9 @@
   }
 
   if (match(V, m_NUWShl(m_Value(Op1), m_ConstantInt(CI))) && canUseSExt(CI)) {
-    int64_t Mult = int64_t(std::pow(int64_t(2), CI->getSExtValue()));
+    if (CI->getSExtValue() < 0 || CI->getSExtValue() >= 64)
+      return {V, IsKnownNonNegative};
+    int64_t Mult = 1 << CI->getSExtValue();
     auto Result = decompose(Op1, Preconditions, IsSigned, DL);
     Result.mul(Mult);
     return Result;


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D145677.503831.patch
Type: text/x-patch
Size: 2396 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20230309/f1b04cb2/attachment.bin>