Merge pull request #2631 from TNorthover/swifterror-noload

FastISel: do not fold a swifterror load into anything.

Author: TNorthover

llvm/lib/CodeGen/SelectionDAG/FastISel.cpp

@@ -2413,6 +2413,12 @@ bool FastISel::tryToFoldLoad(const LoadInst *LI, const Instruction *FoldInst) {
   if (LI->isVolatile())
     return false;
 
+  // Swifterror loads are not actually loads.
+  if (auto AI = dyn_cast<AllocaInst>(LI->getPointerOperand())) {
+    if (AI->isSwiftError())
+      return false;
+  }
+
   // Figure out which vreg this is going into.  If there is no assigned vreg yet
   // then there actually was no reference to it.  Perhaps the load is referenced
   // by a dead instruction.

llvm/test/CodeGen/X86/swifterror-O0.ll

@@ -0,0 +1,20 @@
+; RUN: llc -mtriple=x86_64-apple-darwin -O0 %s -o - | FileCheck %s
+
+define i32 @foo() {
+; CHECK-LABEL: foo:
+; CHECK: cmpq $0, %r12
+
+  %swifterror = alloca swifterror i8*
+  call void @callee(i8** swifterror %swifterror)
+  %err = load i8*, i8** %swifterror
+  %tst = icmp ne i8* %err, null
+  br i1 %tst, label %true, label %false
+
+true:
+  ret i32 0
+
+false:
+  ret i32 1
+}
+
+declare void @callee(i8** swifterror)