Subzero: Use "pxor reg,reg" to load a floating-point scalar 0.0 value.

tests_lit/llvm2ice_tests/undef.ll

 ; This test checks that undef values are represented as zero.
 
 ; RUN: %p2i -i %s --filetype=obj --disassemble --args -O2 \
 ; RUN:   | FileCheck %s
 ; RUN: %p2i -i %s --filetype=obj --disassemble --args -Om1 \
 ; RUN:   | FileCheck %s
 ; RUN: %p2i -i %s --filetype=obj --disassemble --args -O2 -mattr=sse4.1 \
 ; RUN:   | FileCheck %s
 ; RUN: %p2i -i %s --filetype=obj --disassemble --args -Om1 -mattr=sse4.1 \
 ; RUN:   | FileCheck %s
@@ skipping 20 matching lines @@
   ret i32 %ret
 ; CHECK-LABEL: trunc_undef_i64
 ; CHECK: mov eax,0x0
 ; CHECK: ret
 }
 
 define internal float @undef_float() {
 entry:
   ret float undef
 ; CHECK-LABEL: undef_float
-; CHECK: fld DWORD PTR {{.*}} .L$float$00000000
+; xCHECK: fld DWORD PTR {{.*}} .L$float$00000000

[sehr, 2015/11/13 21:49:13]

Delete this.

[Jim Stichnoth, 2015/11/13 22:20:24]

Oops, done.

+; CHECK: pxor [[REG:xmm.]],[[REG]]
 }
 
 define internal <4 x i1> @undef_v4i1() {
 entry:
   ret <4 x i1> undef
 ; CHECK-LABEL: undef_v4i1
 ; CHECK: pxor
 }
 
 define internal <8 x i1> @undef_v8i1() {
@@ skipping 132 matching lines @@
   ret <4 x float> %val
 ; CHECK-LABEL: vector_insertelement_arg1
 ; CHECK: pxor
 }
 
 define internal <4 x float> @vector_insertelement_arg2(<4 x float> %arg) {
 entry:
   %val = insertelement <4 x float> %arg, float undef, i32 0
   ret <4 x float> %val
 ; CHECK-LABEL: vector_insertelement_arg2
-; CHECK: {{movss|insertps}} {{.*}},DWORD PTR {{.*}} .L$float$00000000
+; CHECK: pxor [[REG:xmm.]],[[REG]]
+; CHECK: {{movss|insertps}} {{.*}},[[REG]]
 }
 
 define internal float @vector_extractelement_v4f32_index_0() {
 entry:
   %val = extractelement <4 x float> undef, i32 0
   ret float %val
 ; CHECK-LABEL: vector_extractelement_v4f32_index_0
 ; CHECK: pxor
 }
 
@@ skipping 87 matching lines @@
 }
 
 define internal <4 x float> @vector_select_v4f32_arg2(<4 x i1> %cond,
                                                       <4 x float> %a) {
 entry:
   %val = select <4 x i1> %cond, <4 x float> %a, <4 x float> undef
   ret <4 x float> %val
 ; CHECK-LABEL: vector_select_v4f32_arg2
 ; CHECK: pxor
 }