Convert a subtract into a negate and an add when it helps x86

address folding.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71446 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 25 insertions, 0 deletions

diff --git a/test/CodeGen/X86/lea-neg.ll b/test/CodeGen/X86/lea-neg.ll
new file mode 100644
index 0000000000..61cd75c9cc
--- /dev/null
+++ b/test/CodeGen/X86/lea-neg.ll
@@ -0,0 +1,25 @@
+; RUN: llvm-as < %s | llc -march=x86-64 > %t
+; RUN: grep negl %t | count 1
+; RUN: not grep sub %t
+; RUN: grep mov %t | count 1
+; RUN: grep {leal	-4(} %t | count 1
+
+; ISel the add of -4 with a neg and use an lea for the rest of the
+; arithemtic.
+
+define i32 @test(i32 %x_offs) nounwind readnone {
+entry:
+	%t0 = icmp sgt i32 %x_offs, 4		; <i1> [#uses=1]
+	br i1 %t0, label %bb.nph, label %bb2
+
+bb.nph:		; preds = %entry
+	%tmp = add i32 %x_offs, -5		; <i32> [#uses=1]
+	%tmp6 = lshr i32 %tmp, 2		; <i32> [#uses=1]
+	%tmp7 = mul i32 %tmp6, -4		; <i32> [#uses=1]
+	%tmp8 = add i32 %tmp7, %x_offs		; <i32> [#uses=1]
+	%tmp9 = add i32 %tmp8, -4		; <i32> [#uses=1]
+	ret i32 %tmp9
+
+bb2:		; preds = %entry
+	ret i32 %x_offs
+}