Chris Lattner e5a1426174 optimize bitcast(trunc(bitcast(x))) where the result is a float and 'x'
is a vector to be a vector element extraction.  This allows clang to
compile:

struct S { float A, B, C, D; };
float foo(struct S A) { return A.A + A.B+A.C+A.D; }

into:

_foo:                                   ## @foo
## BB#0:                                ## %entry
	movd	%xmm0, %rax
	shrq	$32, %rax
	movd	%eax, %xmm2
	addss	%xmm0, %xmm2
	movapd	%xmm1, %xmm3
	addss	%xmm2, %xmm3
	movd	%xmm1, %rax
	shrq	$32, %rax
	movd	%eax, %xmm0
	addss	%xmm3, %xmm0
	ret

instead of:

_foo:                                   ## @foo
## BB#0:                                ## %entry
	movd	%xmm0, %rax
	movd	%eax, %xmm0
	shrq	$32, %rax
	movd	%eax, %xmm2
	addss	%xmm0, %xmm2
	movd	%xmm1, %rax
	movd	%eax, %xmm1
	addss	%xmm2, %xmm1
	shrq	$32, %rax
	movd	%eax, %xmm0
	addss	%xmm1, %xmm0
	ret

... eliminating half of the horribleness.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112227 91177308-0d34-0410-b5e6-96231b3b80d8
2010-08-26 21:55:42 +00:00
..

This directory contains test cases for the instcombine transformation.  The
dated tests are actual bug tests, whereas the named tests are used to test
for features that the this pass should be capable of performing.