[PATCH] D72302: [X86] Improve lowering of v2i64 sign bit tests on pre-sse4.2 targets

[Craig Topper via Phabricator via llvm-commits]

craig.topper marked an inline comment as done.
craig.topper added inline comments.


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Comment at: llvm/test/CodeGen/X86/bitcast-vector-bool.ll:432
 ; SSE2-SSSE3:       # %bb.0:
-; SSE2-SSSE3-NEXT:    movdqa {{.*#+}} xmm4 = [2147483648,2147483648]
-; SSE2-SSSE3-NEXT:    pxor %xmm4, %xmm3
-; SSE2-SSSE3-NEXT:    movdqa %xmm4, %xmm5
-; SSE2-SSSE3-NEXT:    pcmpgtd %xmm3, %xmm5
-; SSE2-SSSE3-NEXT:    pshufd {{.*#+}} xmm6 = xmm5[0,0,2,2]
-; SSE2-SSSE3-NEXT:    pcmpeqd %xmm4, %xmm3
-; SSE2-SSSE3-NEXT:    pshufd {{.*#+}} xmm3 = xmm3[1,1,3,3]
-; SSE2-SSSE3-NEXT:    pand %xmm6, %xmm3
-; SSE2-SSSE3-NEXT:    pshufd {{.*#+}} xmm5 = xmm5[1,1,3,3]
-; SSE2-SSSE3-NEXT:    por %xmm3, %xmm5
-; SSE2-SSSE3-NEXT:    pxor %xmm4, %xmm2
-; SSE2-SSSE3-NEXT:    movdqa %xmm4, %xmm3
-; SSE2-SSSE3-NEXT:    pcmpgtd %xmm2, %xmm3
-; SSE2-SSSE3-NEXT:    pshufd {{.*#+}} xmm6 = xmm3[0,0,2,2]
-; SSE2-SSSE3-NEXT:    pcmpeqd %xmm4, %xmm2
-; SSE2-SSSE3-NEXT:    pshufd {{.*#+}} xmm7 = xmm2[1,1,3,3]
-; SSE2-SSSE3-NEXT:    pand %xmm6, %xmm7
-; SSE2-SSSE3-NEXT:    pshufd {{.*#+}} xmm2 = xmm3[1,1,3,3]
-; SSE2-SSSE3-NEXT:    por %xmm7, %xmm2
-; SSE2-SSSE3-NEXT:    packssdw %xmm5, %xmm2
-; SSE2-SSSE3-NEXT:    pxor %xmm4, %xmm1
-; SSE2-SSSE3-NEXT:    movdqa %xmm4, %xmm3
-; SSE2-SSSE3-NEXT:    pcmpgtd %xmm1, %xmm3
-; SSE2-SSSE3-NEXT:    pshufd {{.*#+}} xmm5 = xmm3[0,0,2,2]
-; SSE2-SSSE3-NEXT:    pcmpeqd %xmm4, %xmm1
-; SSE2-SSSE3-NEXT:    pshufd {{.*#+}} xmm1 = xmm1[1,1,3,3]
-; SSE2-SSSE3-NEXT:    pand %xmm5, %xmm1
-; SSE2-SSSE3-NEXT:    pshufd {{.*#+}} xmm3 = xmm3[1,1,3,3]
-; SSE2-SSSE3-NEXT:    por %xmm1, %xmm3
-; SSE2-SSSE3-NEXT:    pxor %xmm4, %xmm0
-; SSE2-SSSE3-NEXT:    movdqa %xmm4, %xmm1
-; SSE2-SSSE3-NEXT:    pcmpgtd %xmm0, %xmm1
-; SSE2-SSSE3-NEXT:    pshufd {{.*#+}} xmm5 = xmm1[0,0,2,2]
-; SSE2-SSSE3-NEXT:    pcmpeqd %xmm4, %xmm0
-; SSE2-SSSE3-NEXT:    pshufd {{.*#+}} xmm0 = xmm0[1,1,3,3]
-; SSE2-SSSE3-NEXT:    pand %xmm5, %xmm0
-; SSE2-SSSE3-NEXT:    pshufd {{.*#+}} xmm1 = xmm1[1,1,3,3]
-; SSE2-SSSE3-NEXT:    por %xmm0, %xmm1
-; SSE2-SSSE3-NEXT:    packssdw %xmm3, %xmm1
-; SSE2-SSSE3-NEXT:    packssdw %xmm2, %xmm1
-; SSE2-SSSE3-NEXT:    packsswb %xmm0, %xmm1
-; SSE2-SSSE3-NEXT:    pmovmskb %xmm1, %eax
+; SSE2-SSSE3-NEXT:    packssdw %xmm3, %xmm2
+; SSE2-SSSE3-NEXT:    packssdw %xmm1, %xmm0
----------------
The new code is simple enough that simplify demanded bits was able to get through it. The movmskb only needs the sign bits from its input and packss doesn't alter sign bits so it was able to prove the compare unnecessary.


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  https://reviews.llvm.org/D72302/new/

https://reviews.llvm.org/D72302