Teach ISel not to optimize 'optnone' functions (revised).

Improvements over r195317:
- Set/restore EnableFastISel flag instead of just running FastISel within
  SelectAllBasicBlocks; the flag is checked in various places, and
  FastISel won't run properly if those places don't do the right thing.
- Test looks for normal ISel versus FastISel behavior, and not
  something more subtle that doesn't work everywhere.

Based on work by Andrea Di Biagio.

llvm-svn: 195491

1 files changed, 42 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/X86/isel-optnone.ll b/llvm/test/CodeGen/X86/isel-optnone.ll
new file mode 100644
index 00000000000..d2f062832e0
--- /dev/null
+++ b/llvm/test/CodeGen/X86/isel-optnone.ll
@@ -0,0 +1,42 @@
+; RUN: llc -O2 -march=x86 < %s | FileCheck %s
+
+define i32* @fooOptnone(i32* %p, i32* %q, i32** %z) #0 {
+entry:
+  %r = load i32* %p
+  %s = load i32* %q
+  %y = load i32** %z
+
+  %t0 = add i32 %r, %s
+  %t1 = add i32 %t0, 1
+  %t2 = getelementptr i32* %y, i32 1
+  %t3 = getelementptr i32* %t2, i32 %t1
+
+  ret i32* %t3
+
+; 'optnone' should use fast-isel which will not produce 'lea'.
+; CHECK-LABEL: fooOptnone:
+; CHECK-NOT:   lea
+; CHECK:       ret
+}
+
+define i32* @fooNormal(i32* %p, i32* %q, i32** %z) #1 {
+entry:
+  %r = load i32* %p
+  %s = load i32* %q
+  %y = load i32** %z
+
+  %t0 = add i32 %r, %s
+  %t1 = add i32 %t0, 1
+  %t2 = getelementptr i32* %y, i32 1
+  %t3 = getelementptr i32* %t2, i32 %t1
+
+  ret i32* %t3
+
+; Normal ISel will produce 'lea'.
+; CHECK-LABEL: fooNormal:
+; CHECK:       lea
+; CHECK:       ret
+}
+
+attributes #0 = { nounwind optnone noinline }
+attributes #1 = { nounwind }