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AVX: go back to using blend (vs. masked store) when possible.

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All of the masked store calls were inhibiting putting values into
registers, which in turn led to a lot of unnecessary stack traffic.
This approach seems to give better code in the end.
This commit is contained in:
Matt Pharr
2011-09-07 11:26:49 -07:00
parent 375f1cb8e8
commit c86128e8ee
4 changed files with 195 additions and 54 deletions
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82
builtins-avx.ll
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@@ -450,38 +450,74 @@ define void @__masked_store_64(<8 x i64>* nocapture, <8 x i64>,
}
;; FIXME: various code elsewhere in the builtins implementations makes
;; calls to the 32/64 bit versions of these, basically assuming that doing
;; so is faster than doing a full call to an actual masked store, which
;; isn't likely to be the case on AVX. So here we provide those functions
;; but then don't actually do what the caller asked for...
declare void @llvm.trap()
define void @__masked_store_blend_8(<8 x i8>* nocapture, <8 x i8>,
<8 x i32>) nounwind alwaysinline {
call void @llvm.trap()
ret void
}
define void @__masked_store_blend_16(<8 x i16>* nocapture, <8 x i16>,
<8 x i32>) nounwind alwaysinline {
call void @llvm.trap()
ret void
}
masked_store_blend_8_16_by_8()
declare <8 x float> @llvm.x86.avx.blendv.ps.256(<8 x float>, <8 x float>,
<8 x float>) nounwind readnone
define void @__masked_store_blend_32(<8 x i32>* nocapture, <8 x i32>,
<8 x i32>) nounwind alwaysinline {
call void @__masked_store_32(<8 x i32> * %0, <8 x i32> %1, <8 x i32> %2)
%mask_as_float = bitcast <8 x i32> %2 to <8 x float>
%oldValue = load <8 x i32>* %0, align 4
%oldAsFloat = bitcast <8 x i32> %oldValue to <8 x float>
%newAsFloat = bitcast <8 x i32> %1 to <8 x float>
%blend = call <8 x float> @llvm.x86.avx.blendv.ps.256(<8 x float> %oldAsFloat,
<8 x float> %newAsFloat,
<8 x float> %mask_as_float)
%blendAsInt = bitcast <8 x float> %blend to <8 x i32>
store <8 x i32> %blendAsInt, <8 x i32>* %0, align 4
ret void
}
define void @__masked_store_blend_64(<8 x i64>* nocapture, <8 x i64>,
<8 x i32>) nounwind alwaysinline {
call void @__masked_store_64(<8 x i64> * %0, <8 x i64> %1, <8 x i32> %2)
define void @__masked_store_blend_64(<8 x i64>* nocapture %ptr, <8 x i64> %new,
<8 x i32> %i32mask) nounwind alwaysinline {
%oldValue = load <8 x i64>* %ptr, align 8
%mask = bitcast <8 x i32> %i32mask to <8 x float>
; Do 4x64-bit blends by doing two <8 x i32> blends, where the <8 x i32> values
; are actually bitcast <4 x i64> values
;
; set up the first four 64-bit values
%old01 = shufflevector <8 x i64> %oldValue, <8 x i64> undef,
<4 x i32> <i32 0, i32 1, i32 2, i32 3>
%old01f = bitcast <4 x i64> %old01 to <8 x float>
%new01 = shufflevector <8 x i64> %new, <8 x i64> undef,
<4 x i32> <i32 0, i32 1, i32 2, i32 3>
%new01f = bitcast <4 x i64> %new01 to <8 x float>
; compute mask--note that the indices are all doubled-up
%mask01 = shufflevector <8 x float> %mask, <8 x float> undef,
<8 x i32> <i32 0, i32 0, i32 1, i32 1,
i32 2, i32 2, i32 3, i32 3>
; and blend them
%result01f = call <8 x float> @llvm.x86.avx.blendv.ps.256(<8 x float> %old01f,
<8 x float> %new01f,
<8 x float> %mask01)
%result01 = bitcast <8 x float> %result01f to <4 x i64>
; and again
%old23 = shufflevector <8 x i64> %oldValue, <8 x i64> undef,
<4 x i32> <i32 4, i32 5, i32 6, i32 7>
%old23f = bitcast <4 x i64> %old23 to <8 x float>
%new23 = shufflevector <8 x i64> %new, <8 x i64> undef,
<4 x i32> <i32 4, i32 5, i32 6, i32 7>
%new23f = bitcast <4 x i64> %new23 to <8 x float>
; compute mask--note that the values are doubled-up...
%mask23 = shufflevector <8 x float> %mask, <8 x float> undef,
<8 x i32> <i32 4, i32 4, i32 5, i32 5,
i32 6, i32 6, i32 7, i32 7>
; and blend them
%result23f = call <8 x float> @llvm.x86.avx.blendv.ps.256(<8 x float> %old23f,
<8 x float> %new23f,
<8 x float> %mask23)
%result23 = bitcast <8 x float> %result23f to <4 x i64>
; reconstruct the final <8 x i64> vector
%final = shufflevector <4 x i64> %result01, <4 x i64> %result23,
<8 x i32> <i32 0, i32 1, i32 2, i32 3,
i32 4, i32 5, i32 6, i32 7>
store <8 x i64> %final, <8 x i64> * %ptr, align 8
ret void
}