[AArch64][GlobalISel] Fall back during AArch64 isel if we have a volatile load.

The tablegen imported patterns for sext(load(a)) don't check for single uses
of the load or delete the original after matching. As a result two loads are
left in the generated code. This particular issue will be fixed by adding
support for a G_SEXTLOAD opcode in future.

There are however other potential issues around this that wouldn't be fixed by
a G_SEXTLOAD, so until we have a proper solution we don't try to handle volatile
loads at all in the AArch64 selector.

Fixes/works around PR36018.

llvm-svn: 323371

1 files changed, 14 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/irtranslator-volatile-load-pr36018.ll b/llvm/test/CodeGen/AArch64/GlobalISel/irtranslator-volatile-load-pr36018.ll
new file mode 100644
index 00000000000..9bda39c9fca
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/irtranslator-volatile-load-pr36018.ll
@@ -0,0 +1,14 @@
+; RUN: llc -O0 -mtriple=aarch64-apple-ios -o - %s | FileCheck %s
+
+@g = global i16 0, align 2
+declare void @bar(i32)
+
+; Check that only one load is generated. We fall back to
+define hidden void @foo() {
+; CHECK-NOT: ldrh
+; CHECK: ldrsh
+  %1 = load volatile i16, i16* @g, align 2
+  %2 = sext i16 %1 to i32
+  call void @bar(i32 %2)
+  ret void
+}