AMDGPU: Fix copying i1 value out of loop with non-uniform exit
Summary:
When an i1-value is defined inside of a loop and used outside of it, we
cannot simply use the SGPR bitmask from the loop's last iteration.
There are also useful and correct cases of an i1-value being copied between
basic blocks, e.g. when a condition is computed outside of a loop and used
inside it. The concept of dominators is not sufficient to capture what is
going on, so I propose the notion of "lane-dominators".
Fixes a bug encountered in Nier: Automata.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103743
Change-Id: If37b969ddc71d823ab3004aeafb9ea050e45bd9a
Reviewers: arsenm, rampitec
Subscribers: kzhuravl, wdng, mgorny, yaxunl, dstuttard, tpr, llvm-commits, t-tye
Differential Revision: https://reviews.llvm.org/D40547
llvm-svn: 329164
2018-04-04 18:57:58 +08:00
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; RUN: llc -march=amdgcn -verify-machineinstrs < %s | FileCheck -check-prefix=SI %s
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; RUN: llc -march=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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; Cannot use an SGPR mask to copy %cc out of the loop, since the mask would
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; only contain the lanes that were active during the last loop iteration.
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;
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; SI: ; %for.body
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2018-06-30 00:26:53 +08:00
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; SI: v_cmp_gt_u32_e64 [[SREG:s\[[0-9]+:[0-9]+\]]], 4,
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; SI: v_cndmask_b32_e64 [[VREG:v[0-9]+]], 0, -1, [[SREG]]
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; SI-NEXT: s_cbranch_vccnz [[ENDIF:BB[0-9_]+]]
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; SI: [[ENDIF]]:
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; SI-NOT: [[VREG]]
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; SI: ; %for.end
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; SI: v_cmp_ne_u32_e32 vcc, 0, [[VREG]]
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AMDGPU: Fix copying i1 value out of loop with non-uniform exit
Summary:
When an i1-value is defined inside of a loop and used outside of it, we
cannot simply use the SGPR bitmask from the loop's last iteration.
There are also useful and correct cases of an i1-value being copied between
basic blocks, e.g. when a condition is computed outside of a loop and used
inside it. The concept of dominators is not sufficient to capture what is
going on, so I propose the notion of "lane-dominators".
Fixes a bug encountered in Nier: Automata.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103743
Change-Id: If37b969ddc71d823ab3004aeafb9ea050e45bd9a
Reviewers: arsenm, rampitec
Subscribers: kzhuravl, wdng, mgorny, yaxunl, dstuttard, tpr, llvm-commits, t-tye
Differential Revision: https://reviews.llvm.org/D40547
llvm-svn: 329164
2018-04-04 18:57:58 +08:00
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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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