Fix PR6497, a bug where we'd fold a load into an addc

node which has a flag.  That flag in turn was used by an
already-selected adde which turned into an ADC32ri8 which
used a selected load which was chained to the load we
folded.  This flag use caused us to form a cycle.  Fix
this by not ignoring chains in IsLegalToFold even in
cases where the isel thinks it can.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97791 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 20 insertions, 0 deletions

diff --git a/test/CodeGen/X86/crash.ll b/test/CodeGen/X86/crash.ll
new file mode 100644
index 0000000..1e13046
--- /dev/null
+++ b/test/CodeGen/X86/crash.ll
@@ -0,0 +1,20 @@
+; RUN: llc -march=x86 %s -o -
+; RUN: llc -march=x86-64 %s -o -
+
+; PR6497
+
+; Chain and flag folding issues.
+define i32 @test1() nounwind ssp {
+entry:
+  %tmp5.i = volatile load i32* undef              ; <i32> [#uses=1]
+  %conv.i = zext i32 %tmp5.i to i64               ; <i64> [#uses=1]
+  %tmp12.i = volatile load i32* undef             ; <i32> [#uses=1]
+  %conv13.i = zext i32 %tmp12.i to i64            ; <i64> [#uses=1]
+  %shl.i = shl i64 %conv13.i, 32                  ; <i64> [#uses=1]
+  %or.i = or i64 %shl.i, %conv.i                  ; <i64> [#uses=1]
+  %add16.i = add i64 %or.i, 256                   ; <i64> [#uses=1]
+  %shr.i = lshr i64 %add16.i, 8                   ; <i64> [#uses=1]
+  %conv19.i = trunc i64 %shr.i to i32             ; <i32> [#uses=1]
+  volatile store i32 %conv19.i, i32* undef
+  ret i32 undef
+}