[SystemZ] Fix truncstore + bswap codegen bug

SystemZTargetLowering::combineSTORE contains code to transform a
combination of STORE + BSWAP into a STRV type instruction.

This transformation is correct for regular stores, but not for
truncating stores.  The routine neglected to check for that case.

Fixes a miscompilation of llvm-objcopy with clang, which caused
test suite failures in the SystemZ multistage build bot.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@313669 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/SystemZ/SystemZISelLowering.cpp b/lib/Target/SystemZ/SystemZISelLowering.cpp
index 1900a00ef26477ecfc962e3ff9252bad2fc22965..9e24a3b9548342743f109afcc3a75d65b64a5b39 100644 (file)
--- a/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ b/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -5225,7 +5225,8 @@ SDValue SystemZTargetLowering::combineSTORE(
   }
   // Combine STORE (BSWAP) into STRVH/STRV/STRVG
   // See comment in combineBSWAP about volatile accesses.
-  if (!SN->isVolatile() &&
+  if (!SN->isTruncatingStore() &&
+      !SN->isVolatile() &&
       Op1.getOpcode() == ISD::BSWAP &&
       Op1.getNode()->hasOneUse() &&
       (Op1.getValueType() == MVT::i16 ||

diff --git a/test/CodeGen/SystemZ/bswap-08.ll b/test/CodeGen/SystemZ/bswap-08.ll
new file mode 100644 (file)
index 0000000..f82b09b
--- /dev/null
+++ b/test/CodeGen/SystemZ/bswap-08.ll
@@ -0,0 +1,17 @@
+; Verify that truncating stores do not use STRV
+;
+; RUN: llc < %s -mtriple=s390x-linux-gnu | FileCheck %s
+
+declare i64 @llvm.bswap.i64(i64)
+
+define void @f1(i32* %x, i64* %y) {
+; CHECK-LABEL: f1:
+; CHECK-NOT: strv
+; CHECK: br %r14
+  %a = load i64, i64* %y, align 8
+  %b = tail call i64 @llvm.bswap.i64(i64 %a)
+  %conv = trunc i64 %b to i32
+  store i32 %conv, i32* %x, align 4
+  ret void
+}
+