[ConstantFolding] Correctly handle failures in ConstantFoldConstantExpressionImpl

Failures in ConstantFoldConstantExpressionImpl were ignored causing
crashes down the line.

This fixes PR28725.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@276827 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 27 insertions, 4 deletions

diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp
index c9adaa7b111..8f67492971d 100644
--- a/lib/Analysis/ConstantFolding.cpp
+++ b/lib/Analysis/ConstantFolding.cpp
@@ -1007,8 +1007,12 @@ Constant *llvm::ConstantFoldInstruction(Instruction *I, const DataLayout &DL,
   for (const Use &OpU : I->operands()) {
     auto *Op = cast<Constant>(&OpU);
     // Fold the Instruction's operands.
-    if (auto *NewCE = dyn_cast<ConstantExpr>(Op))
-      Op = ConstantFoldConstantExpression(NewCE, DL, TLI);
+    if (auto *NewCE = dyn_cast<ConstantExpr>(Op)) {
+      auto *FoldedOp = ConstantFoldConstantExpression(NewCE, DL, TLI);
+      if (!FoldedOp)
+        return nullptr;
+      Op = FoldedOp;
+    }
 
     Ops.push_back(Op);
   }
@@ -1048,8 +1052,13 @@ ConstantFoldConstantExpressionImpl(const ConstantExpr *CE, const DataLayout &DL,
     // Recursively fold the ConstantExpr's operands. If we have already folded
     // a ConstantExpr, we don't have to process it again.
     if (auto *NewCE = dyn_cast<ConstantExpr>(NewC)) {
-      if (FoldedOps.insert(NewCE).second)
-        NewC = ConstantFoldConstantExpressionImpl(NewCE, DL, TLI, FoldedOps);
+      if (FoldedOps.insert(NewCE).second){
+        auto *FoldedC =
+            ConstantFoldConstantExpressionImpl(NewCE, DL, TLI, FoldedOps);
+        if (!FoldedC)
+          return nullptr;
+        NewC = FoldedC;
+      }
     }
     Ops.push_back(NewC);
   }
diff --git a/test/Transforms/InstSimplify/pr28725.ll b/test/Transforms/InstSimplify/pr28725.ll
new file mode 100644
index 00000000000..bc6b30a5885
--- /dev/null
+++ b/test/Transforms/InstSimplify/pr28725.ll
@@ -0,0 +1,14 @@
+; RUN: opt -S -instsimplify < %s | FileCheck %s
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+%S = type { i16, i32 }
+
+define <2 x i16> @test1() {
+entry:
+  %b = insertelement <2 x i16> <i16 undef, i16 0>, i16 extractvalue (%S select (i1 icmp eq (i16 extractelement (<2 x i16> bitcast (<1 x i32> <i32 1> to <2 x i16>), i32 0), i16 0), %S zeroinitializer, %S { i16 0, i32 1 }), 0), i32 0
+  ret <2 x i16> %b
+}
+
+; CHECK-LABEL: @test1(
+; CHECK: %[[ie:.*]] = insertelement <2 x i16> <i16 undef, i16 0>, i16 extractvalue (%S select (i1 icmp eq (i16 extractelement (<2 x i16> bitcast (<1 x i32> <i32 1> to <2 x i16>), i32 0), i16 0), %S zeroinitializer, %S { i16 0, i32 1 }), 0), i32 0
+; CHECK: ret <2 x i16> %[[ie]]