Make a transformation added in 63266 a bit less aggressive.

It was transforming (x&y)==y to (x&y)!=0 in the case where
y is variable and known to have at most one bit set (e.g. z&1).
This is not correct; the expressions are not equivalent when y==0.
I believe this patch salvages what can be salvaged, including
all the cases in bt.ll.  Dan, please review.
Fixes gcc.c-torture/execute/20040709-[12].c



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@64314 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 70 insertions, 0 deletions

diff --git a/test/CodeGen/X86/nobt.ll b/test/CodeGen/X86/nobt.ll
new file mode 100644
index 00000000000..55294280f5c
--- /dev/null
+++ b/test/CodeGen/X86/nobt.ll
@@ -0,0 +1,70 @@
+; RUN: llvm-as < %s | llc -march=x86 | not grep btl
+
+; This tests some cases where BT must not be generated.  See also bt.ll.
+; Fixes 20040709-[12].c in gcc testsuite.
+
+define void @test2(i32 %x, i32 %n) nounwind {
+entry:
+        %tmp1 = and i32 %x, 1
+        %tmp2 = urem i32 %tmp1, 15
+	%tmp3 = and i32 %tmp2, 1		; <i32> [#uses=1]
+	%tmp4 = icmp eq i32 %tmp3, %tmp2	; <i1> [#uses=1]
+	br i1 %tmp4, label %bb, label %UnifiedReturnBlock
+
+bb:		; preds = %entry
+	call void @foo()
+	ret void
+
+UnifiedReturnBlock:		; preds = %entry
+	ret void
+}
+
+define void @test3(i32 %x, i32 %n) nounwind {
+entry:
+        %tmp1 = and i32 %x, 1
+        %tmp2 = urem i32 %tmp1, 15
+	%tmp3 = and i32 %tmp2, 1		; <i32> [#uses=1]
+	%tmp4 = icmp eq i32 %tmp2, %tmp3	; <i1> [#uses=1]
+	br i1 %tmp4, label %bb, label %UnifiedReturnBlock
+
+bb:		; preds = %entry
+	call void @foo()
+	ret void
+
+UnifiedReturnBlock:		; preds = %entry
+	ret void
+}
+
+define void @test4(i32 %x, i32 %n) nounwind {
+entry:
+        %tmp1 = and i32 %x, 1
+        %tmp2 = urem i32 %tmp1, 15
+	%tmp3 = and i32 %tmp2, 1		; <i32> [#uses=1]
+	%tmp4 = icmp ne i32 %tmp2, %tmp3	; <i1> [#uses=1]
+	br i1 %tmp4, label %bb, label %UnifiedReturnBlock
+
+bb:		; preds = %entry
+	call void @foo()
+	ret void
+
+UnifiedReturnBlock:		; preds = %entry
+	ret void
+}
+
+define void @test5(i32 %x, i32 %n) nounwind {
+entry:
+        %tmp1 = and i32 %x, 1
+        %tmp2 = urem i32 %tmp1, 15
+	%tmp3 = and i32 %tmp2, 1		; <i32> [#uses=1]
+	%tmp4 = icmp ne i32 %tmp2, %tmp3	; <i1> [#uses=1]
+	br i1 %tmp4, label %bb, label %UnifiedReturnBlock
+
+bb:		; preds = %entry
+	call void @foo()
+	ret void
+
+UnifiedReturnBlock:		; preds = %entry
+	ret void
+}
+
+declare void @foo()