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776a459079
Summary: Instead of writing boolean values temporarily into 32-bit VGPRs if they are involved in PHIs or are observed from outside a loop, we use bitwise masking operations to combine lane masks in a way that is consistent with wave control flow. Move SIFixSGPRCopies to before this pass, since that pass incorrectly attempts to move SGPR phis to VGPRs. This should recover most of the code quality that was lost with the bug fix in "AMDGPU: Remove PHI loop condition optimization". There are still some relevant cases where code quality could be improved, in particular: - We often introduce redundant masks with EXEC. Ideally, we'd have a generic computeKnownBits-like analysis to determine whether masks are already masked by EXEC, so we can avoid this masking both here and when lowering uniform control flow. - The criterion we use to determine whether a def is observed from outside a loop is conservative: it doesn't check whether (loop) branch conditions are uniform. Change-Id: Ibabdb373a7510e426b90deef00f5e16c5d56e64b Reviewers: arsenm, rampitec, tpr Subscribers: kzhuravl, jvesely, wdng, mgorny, yaxunl, dstuttard, t-tye, eraman, llvm-commits Differential Revision: https://reviews.llvm.org/D53496 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@345719 91177308-0d34-0410-b5e6-96231b3b80d8
57 lines
1.9 KiB
LLVM
57 lines
1.9 KiB
LLVM
; RUN: llc -mtriple=amdgcn-- -verify-machineinstrs < %s | FileCheck -check-prefix=SI %s
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; RUN: llc -mtriple=amdgcn-- -mcpu=tonga -verify-machineinstrs < %s | FileCheck -check-prefix=SI %s
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; SI-LABEL: {{^}}i1_copy_from_loop:
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;
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; SI: ; %for.body
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; SI: v_cmp_gt_u32_e64 [[CC_SREG:s\[[0-9]+:[0-9]+\]]], 4,
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; SI-DAG: s_andn2_b64 [[CC_ACCUM:s\[[0-9]+:[0-9]+\]]], [[CC_ACCUM]], exec
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; SI-DAG: s_and_b64 [[CC_MASK:s\[[0-9]+:[0-9]+\]]], [[CC_SREG]], exec
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; SI: s_or_b64 [[CC_ACCUM]], [[CC_ACCUM]], [[CC_MASK]]
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; SI: ; %Flow1
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; SI: s_or_b64 [[CC_ACCUM]], [[CC_ACCUM]], exec
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; SI: ; %Flow
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; SI-DAG: s_andn2_b64 [[LCSSA_ACCUM:s\[[0-9]+:[0-9]+\]]], [[LCSSA_ACCUM]], exec
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; SI-DAG: s_and_b64 [[CC_MASK2:s\[[0-9]+:[0-9]+\]]], [[CC_ACCUM]], exec
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; SI: s_or_b64 [[LCSSA_ACCUM]], [[LCSSA_ACCUM]], [[CC_MASK2]]
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; SI: ; %for.end
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; SI: s_and_saveexec_b64 {{s\[[0-9]+:[0-9]+\]}}, [[LCSSA_ACCUM]]
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define amdgpu_ps void @i1_copy_from_loop(<4 x i32> inreg %rsrc, i32 %tid) {
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entry:
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br label %for.body
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for.body:
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%i = phi i32 [0, %entry], [%i.inc, %end.loop]
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%cc = icmp ult i32 %i, 4
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br i1 %cc, label %mid.loop, label %for.end
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mid.loop:
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%v = call float @llvm.amdgcn.buffer.load.f32(<4 x i32> %rsrc, i32 %tid, i32 %i, i1 false, i1 false)
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%cc2 = fcmp oge float %v, 0.0
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br i1 %cc2, label %end.loop, label %for.end
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end.loop:
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%i.inc = add i32 %i, 1
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br label %for.body
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for.end:
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br i1 %cc, label %if, label %end
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if:
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call void @llvm.amdgcn.exp.f32(i32 0, i32 15, float undef, float undef, float undef, float undef, i1 true, i1 true)
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br label %end
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end:
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ret void
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}
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declare float @llvm.amdgcn.buffer.load.f32(<4 x i32>, i32, i32, i1, i1) #0
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declare void @llvm.amdgcn.exp.f32(i32, i32, float, float, float, float, i1, i1) #1
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attributes #0 = { nounwind readonly }
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attributes #1 = { nounwind inaccessiblememonly }
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