[PATCH] D74088: [x86] form broadcast of scalar memop even with >1 use

[Sanjay Patel via Phabricator via llvm-commits]

spatel marked an inline comment as done.
spatel added inline comments.


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Comment at: llvm/test/CodeGen/X86/vector-reduce-fadd.ll:1109
 define double @test_v16f64(double %a0, <16 x double> %a1) {
-; SSE-LABEL: test_v16f64:
-; SSE:       # %bb.0:
-; SSE-NEXT:    movapd {{[0-9]+}}(%rsp), %xmm8
-; SSE-NEXT:    addsd %xmm1, %xmm0
-; SSE-NEXT:    unpckhpd {{.*#+}} xmm1 = xmm1[1,1]
-; SSE-NEXT:    addsd %xmm1, %xmm0
-; SSE-NEXT:    addsd %xmm2, %xmm0
-; SSE-NEXT:    unpckhpd {{.*#+}} xmm2 = xmm2[1,1]
-; SSE-NEXT:    addsd %xmm2, %xmm0
-; SSE-NEXT:    addsd %xmm3, %xmm0
-; SSE-NEXT:    unpckhpd {{.*#+}} xmm3 = xmm3[1,1]
-; SSE-NEXT:    addsd %xmm3, %xmm0
-; SSE-NEXT:    addsd %xmm4, %xmm0
-; SSE-NEXT:    unpckhpd {{.*#+}} xmm4 = xmm4[1,1]
-; SSE-NEXT:    addsd %xmm4, %xmm0
-; SSE-NEXT:    addsd %xmm5, %xmm0
-; SSE-NEXT:    unpckhpd {{.*#+}} xmm5 = xmm5[1,1]
-; SSE-NEXT:    addsd %xmm5, %xmm0
-; SSE-NEXT:    addsd %xmm6, %xmm0
-; SSE-NEXT:    unpckhpd {{.*#+}} xmm6 = xmm6[1,1]
-; SSE-NEXT:    addsd %xmm6, %xmm0
-; SSE-NEXT:    addsd %xmm7, %xmm0
-; SSE-NEXT:    unpckhpd {{.*#+}} xmm7 = xmm7[1,1]
-; SSE-NEXT:    addsd %xmm7, %xmm0
-; SSE-NEXT:    addsd %xmm8, %xmm0
-; SSE-NEXT:    unpckhpd {{.*#+}} xmm8 = xmm8[1,1]
-; SSE-NEXT:    addsd %xmm8, %xmm0
-; SSE-NEXT:    retq
+; SSE2-LABEL: test_v16f64:
+; SSE2:       # %bb.0:
----------------
spatel wrote:
> I haven't stepped through this or the next test diff to see why it changed. Anyone know why SSE2/41 would differ here?
I stepped through this with debug spew - with SSE4.1, we are using X86ISD::MOVDDUP to splat an f64 from memory. That node eventually gets combined away though. 

This is seemingly a win because we removed 2 instructions for the SSE4.1 version - an explicit load with movapd and an unpckhpd.


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  https://reviews.llvm.org/D74088/new/

https://reviews.llvm.org/D74088