[x86] reassociate integer multiplies using machine combiner pass

Add i16, i32, i64 imul machine instructions to the list of reassociation
candidates.

A new bit of logic is needed to handle integer instructions: they have an
implicit EFLAGS operand, so we have to make sure it's dead in order to do
any reassociation with integer ops.

Differential Revision: http://reviews.llvm.org/D11660

llvm-svn: 243756

1 files changed, 43 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/X86/machine-combiner-int.ll b/llvm/test/CodeGen/X86/machine-combiner-int.ll
new file mode 100644
index 00000000000..2f3944f98b0
--- /dev/null
+++ b/llvm/test/CodeGen/X86/machine-combiner-int.ll
@@ -0,0 +1,43 @@
+; RUN: llc -mtriple=x86_64-unknown-unknown -mcpu=x86-64 < %s | FileCheck %s
+
+; Verify that integer multiplies are reassociated. The first multiply in 
+; each test should be independent of the result of the preceding add (lea).
+
+define i16 @reassociate_muls_i16(i16 %x0, i16 %x1, i16 %x2, i16 %x3) {
+; CHECK-LABEL: reassociate_muls_i16:
+; CHECK:       # BB#0:
+; CHECK-NEXT:    leal   (%rdi,%rsi), %eax
+; CHECK-NEXT:    imull  %ecx, %edx
+; CHECK-NEXT:    imull  %edx, %eax
+; CHECK-NEXT:    retq
+  %t0 = add i16 %x0, %x1
+  %t1 = mul i16 %x2, %t0
+  %t2 = mul i16 %x3, %t1
+  ret i16 %t2
+}
+
+define i32 @reassociate_muls_i32(i32 %x0, i32 %x1, i32 %x2, i32 %x3) {
+; CHECK-LABEL: reassociate_muls_i32:
+; CHECK:       # BB#0:
+; CHECK-NEXT:    leal   (%rdi,%rsi), %eax
+; CHECK-NEXT:    imull  %ecx, %edx
+; CHECK-NEXT:    imull  %edx, %eax
+; CHECK-NEXT:    retq
+  %t0 = add i32 %x0, %x1
+  %t1 = mul i32 %x2, %t0
+  %t2 = mul i32 %x3, %t1
+  ret i32 %t2
+}
+
+define i64 @reassociate_muls_i64(i64 %x0, i64 %x1, i64 %x2, i64 %x3) {
+; CHECK-LABEL: reassociate_muls_i64:
+; CHECK:       # BB#0:
+; CHECK-NEXT:    leaq   (%rdi,%rsi), %rax
+; CHECK-NEXT:    imulq  %rcx, %rdx
+; CHECK-NEXT:    imulq  %rdx, %rax
+; CHECK-NEXT:    retq
+  %t0 = add i64 %x0, %x1
+  %t1 = mul i64 %x2, %t0
+  %t2 = mul i64 %x3, %t1
+  ret i64 %t2
+}