Lower multiply-negate operation to mneg on AArch64

This patch pattern matches code such as-
neg	 w8, w8
mul	 w8, w9, w8
to
mneg	 w8, w8, w9

Review: http://reviews.llvm.org/D6754
llvm-svn: 224706

2 files changed, 19 insertions, 0 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.td b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
index 01a01e059a5..3f1dbe0bfc0 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
@@ -657,6 +657,10 @@ def : Pat<(i32 (ineg (mul GPR32:$Rn, GPR32:$Rm))),
           (MSUBWrrr GPR32:$Rn, GPR32:$Rm, WZR)>;
 def : Pat<(i64 (ineg (mul GPR64:$Rn, GPR64:$Rm))),
           (MSUBXrrr GPR64:$Rn, GPR64:$Rm, XZR)>;
+def : Pat<(i32 (mul (ineg GPR32:$Rn), GPR32:$Rm)),
+          (MSUBWrrr GPR32:$Rn, GPR32:$Rm, WZR)>;
+def : Pat<(i64 (mul (ineg GPR64:$Rn), GPR64:$Rm)),
+          (MSUBXrrr GPR64:$Rn, GPR64:$Rm, XZR)>;
 } // AddedComplexity = 7
 
 let AddedComplexity = 5 in {
diff --git a/llvm/test/CodeGen/AArch64/dp-3source.ll b/llvm/test/CodeGen/AArch64/dp-3source.ll
index 22bd4a844e1..bd96ec728f5 100644
--- a/llvm/test/CodeGen/AArch64/dp-3source.ll
+++ b/llvm/test/CodeGen/AArch64/dp-3source.ll
@@ -161,3 +161,18 @@ define i64 @test_umnegl(i32 %lhs, i32 %rhs) {
 ; CHECK: umnegl {{x[0-9]+}}, {{w[0-9]+}}, {{w[0-9]+}}
   ret i64 %res
 }
+
+@a = common global i32 0, align 4
+@b = common global i32 0, align 4
+@c = common global i32 0, align 4
+
+define void @test_mneg(){
+; CHECK-LABEL: test_mneg:
+  %1 = load i32* @a, align 4
+  %2 = load i32* @b, align 4
+  %3 = sub i32 0, %1
+  %4 = mul i32 %2, %3
+  store i32 %4, i32* @c, align 4
+; CHECK: mneg {{w[0-9]+}}, {{w[0-9]+}}, {{w[0-9]+}}
+  ret void
+}