[ARM] Hoist fabs/fneg above a conversion to float.

This is especially visible in softfp mode, for example in the implementation of libm fabs/fneg functions. If we have:

%1 = vmovdrr r0, r1
%2 = fabs %1

then move the fabs before the vmovdrr:

%1 = and r1, #0x7FFFFFFF
%2 = vmovdrr r0, r1

This is never a lose, and could be a serious win because the vmovdrr may be followed by a vmovrrd, which would enable us to remove the conversion into FPRs completely.

We already do this for f32, but not for f64. Tests are added for both.

llvm-svn: 246360

1 files changed, 41 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/ARM/softfp-fabs-fneg.ll b/llvm/test/CodeGen/ARM/softfp-fabs-fneg.ll
new file mode 100644
index 00000000000..b608fb84021
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/softfp-fabs-fneg.ll
@@ -0,0 +1,41 @@
+; RUN: llc -mtriple=armv7 < %s | FileCheck %s --check-prefix=CHECK-ARM --check-prefix=CHECK
+; RUN: llc -mtriple=thumbv7 < %s | FileCheck %s --check-prefix=CHECK-THUMB --check-prefix=CHECK
+
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv7--"
+
+define double @f(double %a) {
+  ; CHECK-LABEL: f:
+  ; CHECK: bfc r1, #31, #1
+  ; CHECK-NEXT: bx lr
+  %x = call double @llvm.fabs.f64(double %a) readnone
+  ret double %x
+}
+
+define float @g(float %a) {
+  ; CHECK-LABEL: g:
+  ; CHECK-THUMB: bic r0, r0, #-2147483648
+  ; CHECK-ARM: bfc r0, #31, #1
+  ; CHECK-NEXT: bx lr
+  %x = call float @llvm.fabs.f32(float %a) readnone
+  ret float %x
+}
+
+define double @h(double %a) {
+  ; CHECK-LABEL: h:
+  ; CHECK: eor r1, r1, #-2147483648
+  ; CHECK-NEXT: bx lr
+  %x = fsub nsz double -0.0, %a
+  ret double %x
+}
+
+define float @i(float %a) {
+  ; CHECK-LABEL: i:
+  ; CHECK: eor r0, r0, #-2147483648
+  ; CHECK-NEXT: bx lr
+  %x = fsub nsz float -0.0, %a
+  ret float %x
+}
+
+declare double @llvm.fabs.f64(double) readnone
+declare float @llvm.fabs.f32(float) readnone