diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt index 060552b93de..fa37a2a047f 100644 --- a/lib/Target/X86/README.txt +++ b/lib/Target/X86/README.txt @@ -673,3 +673,34 @@ of a v4sf value. Better codegen for vector_shuffles like this { x, 0, 0, 0 } or { x, 0, x, 0}. Perhaps use pxor / xorp* to clear a XMM register first? +//===---------------------------------------------------------------------===// + +Adding to the list of cmp / test poor codegen issues: + +int test(__m128 *A, __m128 *B) { + if (_mm_comige_ss(*A, *B)) + return 3; + else + return 4; +} + +_test: + movl 8(%esp), %eax + movaps (%eax), %xmm0 + movl 4(%esp), %eax + movaps (%eax), %xmm1 + comiss %xmm0, %xmm1 + setae %al + movzbl %al, %ecx + movl $3, %eax + movl $4, %edx + cmpl $0, %ecx + cmove %edx, %eax + ret + +Note the setae, movzbl, cmpl, cmove can be replaced with a single cmovae. There +are a number of issues. 1) We are introducing a setcc between the result of the +intrisic call and select. 2) The intrinsic is expected to produce a i32 value +so a any extend (which becomes a zero extend) is added. + +We probably need some kind of target DAG combine hook to fix this.