[FastISel][X86] Optimize selects when the condition comes from a compare.

Optimize the select instructions sequence to use the EFLAGS directly from a
compare when possible.

llvm-svn: 211543

1 files changed, 62 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/X86/fast-isel-select-cmov.ll b/llvm/test/CodeGen/X86/fast-isel-select-cmov.ll
new file mode 100644
index 00000000000..8008e283ad6
--- /dev/null
+++ b/llvm/test/CodeGen/X86/fast-isel-select-cmov.ll
@@ -0,0 +1,62 @@
+; RUN: llc < %s -fast-isel -fast-isel-abort -mtriple=x86_64-apple-darwin10                  | FileCheck %s
+
+; Test conditional move for the supported types (i16, i32, and i32) and
+; conditon input (argument or cmp). Currently i8 is not supported.
+
+define zeroext i16 @select_cmov_i16(i1 zeroext %cond, i16 zeroext %a, i16 zeroext %b) {
+; CHECK-LABEL: select_cmov_i16
+; CHECK:       testb   $1, %dil
+; CHECK-NEXT:  cmovew  %dx, %si
+; CHECK-NEXT:  movzwl  %si, %eax
+  %1 = select i1 %cond, i16 %a, i16 %b
+  ret i16 %1
+}
+
+define zeroext i16 @select_cmp_cmov_i16(i16 zeroext %a, i16 zeroext %b) {
+; CHECK-LABEL: select_cmp_cmov_i16
+; CHECK:       cmpw    %si, %di
+; CHECK-NEXT:  cmovbw  %di, %si
+; CHECK-NEXT:  movzwl  %si, %eax
+  %1 = icmp ult i16 %a, %b
+  %2 = select i1 %1, i16 %a, i16 %b
+  ret i16 %2
+}
+
+define i32 @select_cmov_i32(i1 zeroext %cond, i32 %a, i32 %b) {
+; CHECK-LABEL: select_cmov_i32
+; CHECK:       testb   $1, %dil
+; CHECK-NEXT:  cmovel  %edx, %esi
+; CHECK-NEXT:  movl    %esi, %eax
+  %1 = select i1 %cond, i32 %a, i32 %b
+  ret i32 %1
+}
+
+define i32 @select_cmp_cmov_i32(i32 %a, i32 %b) {
+; CHECK-LABEL: select_cmp_cmov_i32
+; CHECK:       cmpl    %esi, %edi
+; CHECK-NEXT:  cmovbl  %edi, %esi
+; CHECK-NEXT:  movl    %esi, %eax
+  %1 = icmp ult i32 %a, %b
+  %2 = select i1 %1, i32 %a, i32 %b
+  ret i32 %2
+}
+
+define i64 @select_cmov_i64(i1 zeroext %cond, i64 %a, i64 %b) {
+; CHECK-LABEL: select_cmov_i64
+; CHECK:       testb   $1, %dil
+; CHECK-NEXT:  cmoveq  %rdx, %rsi
+; CHECK-NEXT:  movq    %rsi, %rax
+  %1 = select i1 %cond, i64 %a, i64 %b
+  ret i64 %1
+}
+
+define i64 @select_cmp_cmov_i64(i64 %a, i64 %b) {
+; CHECK-LABEL: select_cmp_cmov_i64
+; CHECK:       cmpq    %rsi, %rdi
+; CHECK-NEXT:  cmovbq  %rdi, %rsi
+; CHECK-NEXT:  movq    %rsi, %rax
+  %1 = icmp ult i64 %a, %b
+  %2 = select i1 %1, i64 %a, i64 %b
+  ret i64 %2
+}
+