Implement some dag combines that allow doing fneg/fabs/fcopysign in integer

registers if used by a bitconvert or using a bitconvert.  This allows us to
avoid constant pool loads and use cheaper integer instructions when the
values come from or end up in integer regs anyway.  For example, we now 
compile CodeGen/X86/fp-in-intregs.ll to:

_test1:
	movl	$2147483648, %eax
	xorl	4(%esp), %eax
	ret
_test2:
	movl	$1065353216, %eax
	orl	4(%esp), %eax
	andl	$3212836864, %eax
	ret

Instead of:
_test1:
	movss	4(%esp), %xmm0
	xorps	LCPI2_0, %xmm0
	movd	%xmm0, %eax
	ret
_test2:
	movss	4(%esp), %xmm0
	andps	LCPI3_0, %xmm0
	movss	LCPI3_1, %xmm1
	andps	LCPI3_2, %xmm1
	orps	%xmm0, %xmm1
	movd	%xmm1, %eax
	ret

bitconverts can happen due to various calling conventions that require
fp values to passed in integer regs in some cases, e.g. when returning
a complex.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46414 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 21 insertions, 0 deletions

diff --git a/test/CodeGen/X86/fp-in-intregs.ll b/test/CodeGen/X86/fp-in-intregs.ll
new file mode 100644
index 0000000..1e3ea89
--- /dev/null
+++ b/test/CodeGen/X86/fp-in-intregs.ll
@@ -0,0 +1,21 @@
+; RUN: llvm-as < %s | llc -march=x86 -mcpu=yonah | not egrep {\(\(xor\|and\)ps\|movd\)}
+
+; These operations should be done in integer registers, eliminating constant
+; pool loads, movd's etc.
+
+define i32 @test1(float %x) nounwind  {
+entry:
+	%tmp2 = sub float -0.000000e+00, %x		; <float> [#uses=1]
+	%tmp210 = bitcast float %tmp2 to i32		; <i32> [#uses=1]
+	ret i32 %tmp210
+}
+
+define i32 @test2(float %x) nounwind  {
+entry:
+	%tmp2 = tail call float @copysignf( float 1.000000e+00, float %x ) nounwind readnone 		; <float> [#uses=1]
+	%tmp210 = bitcast float %tmp2 to i32		; <i32> [#uses=1]
+	ret i32 %tmp210
+}
+
+declare float @copysignf(float, float) nounwind readnone 
+