[AMDGPU] Fixed WWM bug in block otherwise entirely in WQM

[tpr]

Summary

For a block with WQM on entry and exit and containing no exact mode
code, but containing some WWM code, the WQM pass forgot to process the
block at all and so did not insert code to enter and leave WWM.

This commit fixes that.

Change-Id: I044792eead1293bed4203fb26ce75f47878afeb6

[tpr]

Ping.

[nhaehnle]

Oops :)
LGTM.

llvm/trunk/lib/Target/AMDGPU/SIWholeQuadMode.cpp

if (MachineInstr *PrevMI = MI.getPrevNode()) {
     }
   }
 
   // Propagate WQM flag to instruction inputs
   assert(!(II.Needs & StateExact));
 
   if (II.Needs != 0)
     markInstructionUses(MI, II.Needs, Worklist);
+
+  // Ensure we process a block containing WWM, even if it does not require any
+  // WQM transitions.
+  if (II.Needs & StateWWM)
+    BI.Needs |= StateWWM;
 }
 
 void SIWholeQuadMode::propagateBlock(MachineBasicBlock &MBB,
                                      std::vector<WorkItem>& Worklist) {
   BlockInfo BI = Blocks[&MBB]; // Make a copy to prevent dangling references.
 
   // Propagate through instructions
   if (!MBB.empty()) {

llvm/trunk/test/CodeGen/AMDGPU/wqm.ll

else:
   br label %end
 
 end:
   %r = phi <4 x float> [ %r.if, %if ], [ %r.else, %else ]
   call void @llvm.amdgcn.buffer.store.f32(float 1.0, <4 x i32> undef, i32 %idx, i32 0, i1 0, i1 0)
   ret <4 x float> %r
 }
 
+; Check a case of a block being entirely WQM except for a bit of WWM.
+; There was a bug where it forgot to enter and leave WWM.
+;
+;CHECK-LABEL: {{^}}test_wwm_within_wqm:
+;CHECK: %IF
+;CHECK: s_or_saveexec_b64 {{.*}}, -1
+;CHECK: ds_swizzle
+;
+define amdgpu_ps float @test_wwm_within_wqm(<8 x i32> inreg %rsrc, <4 x i32> inreg %sampler, i32 %c, i32 %z, float %data) {
+main_body:
+  %c.bc = bitcast i32 %c to float
+  %tex = call <4 x float> @llvm.amdgcn.image.sample.v4f32.f32.v8i32(float %c.bc, <8 x i32> %rsrc, <4 x i32> %sampler, i32 15, i1 false, i1 false, i1 false, i1 false, i1 false) #0
+  %dtex = call <4 x float> @llvm.amdgcn.image.sample.v4f32.v4f32.v8i32(<4 x float> %tex, <8 x i32> %rsrc, <4 x i32> %sampler, i32 15, i1 false, i1 false, i1 false, i1 false, i1 false) #0
+  %cmp = icmp eq i32 %z, 0
+  br i1 %cmp, label %IF, label %ENDIF
+
+IF:
+  %dataf = extractelement <4 x float> %dtex, i32 0
+  %data1 = fptosi float %dataf to i32
+  %data2 = call i32 @llvm.amdgcn.set.inactive.i32(i32 %data1, i32 0)
+  %data3 = call i32 @llvm.amdgcn.ds.swizzle(i32 %data2, i32 2079)
+  %data4 = call i32 @llvm.amdgcn.wwm.i32(i32 %data3)
+  %data4f = sitofp i32 %data4 to float
+  br label %ENDIF
+
+ENDIF:
+  %r = phi float [ %data4f, %IF ], [ 0.0, %main_body ]
+  ret float %r
+}
+
 declare void @llvm.amdgcn.exp.f32(i32, i32, float, float, float, float, i1, i1) #1
 declare void @llvm.amdgcn.image.store.v4f32.v4i32.v8i32(<4 x float>, <4 x i32>, <8 x i32>, i32, i1, i1, i1, i1) #1
 declare void @llvm.amdgcn.buffer.store.f32(float, <4 x i32>, i32, i32, i1, i1) #2
 declare void @llvm.amdgcn.buffer.store.v4f32(<4 x float>, <4 x i32>, i32, i32, i1, i1) #2
 declare <4 x float> @llvm.amdgcn.image.load.v4f32.v4i32.v8i32(<4 x i32>, <8 x i32>, i32, i1, i1, i1, i1) #3
 declare float @llvm.amdgcn.buffer.load.f32(<4 x i32>, i32, i32, i1, i1) #3
 declare <4 x float> @llvm.amdgcn.image.sample.v4f32.f32.v8i32(float, <8 x i32>, <4 x i32>, i32, i1, i1, i1, i1, i1) #3
 declare <4 x float> @llvm.amdgcn.image.sample.v4f32.v2f32.v8i32(<2 x float>, <8 x i32>, <4 x i32>, i32, i1, i1, i1, i1, i1) #3
 declare <4 x float> @llvm.amdgcn.image.sample.v4f32.v4f32.v8i32(<4 x float>, <8 x i32>, <4 x i32>, i32, i1, i1, i1, i1, i1) #3
 declare void @llvm.AMDGPU.kill(float) #1
 declare float @llvm.amdgcn.wqm.f32(float) #3
 declare i32 @llvm.amdgcn.wqm.i32(i32) #3
 declare float @llvm.amdgcn.wwm.f32(float) #3
 declare i32 @llvm.amdgcn.wwm.i32(i32) #3
 declare i32 @llvm.amdgcn.set.inactive.i32(i32, i32) #4
 declare i32 @llvm.amdgcn.mbcnt.lo(i32, i32) #3
 declare i32 @llvm.amdgcn.mbcnt.hi(i32, i32) #3
 declare <2 x half> @llvm.amdgcn.cvt.pkrtz(float, float) #3
 declare void @llvm.amdgcn.exp.compr.v2f16(i32, i32, <2 x half>, <2 x half>, i1, i1) #1
 declare float @llvm.amdgcn.interp.p1(float, i32, i32, i32) #2
 declare float @llvm.amdgcn.interp.p2(float, float, i32, i32, i32) #2
+declare i32 @llvm.amdgcn.ds.swizzle(i32, i32)
 
 attributes #1 = { nounwind }
 attributes #2 = { nounwind readonly }
 attributes #3 = { nounwind readnone }
 attributes #4 = { nounwind readnone convergent }
 attributes #5 = { "amdgpu-ps-wqm-outputs" }
 attributes #6 = { nounwind "InitialPSInputAddr"="2" }