[llvm] r269391 - AMDGPU: Remove verifier check for scc live ins

[Matt Arsenault via llvm-commits]

Author: arsenm
Date: Thu May 12 23:15:48 2016
New Revision: 269391

URL: http://llvm.org/viewvc/llvm-project?rev=269391&view=rev
Log:
AMDGPU: Remove verifier check for scc live ins

We only really need this to be true for SIFixSGPRCopies.
I'm not sure there's any way this could happen before that point.

Fixes a case where MachineCSE could introduce a cross block
scc use.

Modified:
    llvm/trunk/lib/Target/AMDGPU/SIInstrInfo.cpp
    llvm/trunk/test/CodeGen/AMDGPU/uniform-cfg.ll

Modified: llvm/trunk/lib/Target/AMDGPU/SIInstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AMDGPU/SIInstrInfo.cpp?rev=269391&r1=269390&r2=269391&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AMDGPU/SIInstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/AMDGPU/SIInstrInfo.cpp Thu May 12 23:15:48 2016
@@ -1489,16 +1489,6 @@ bool SIInstrInfo::verifyInstruction(cons
   int Src1Idx = AMDGPU::getNamedOperandIdx(Opcode, AMDGPU::OpName::src1);
   int Src2Idx = AMDGPU::getNamedOperandIdx(Opcode, AMDGPU::OpName::src2);
 
-  // Make sure we don't have SCC live-ins to basic blocks.  moveToVALU assumes
-  // all SCC users are in the same blocks as their defs.
-  const MachineBasicBlock *MBB = MI->getParent();
-  if (MI == &MBB->front()) {
-    if (MBB->isLiveIn(AMDGPU::SCC)) {
-      ErrInfo = "scc register cannot be live across blocks.";
-      return false;
-    }
-  }
-
   // Make sure the number of operands is correct.
   const MCInstrDesc &Desc = get(Opcode);
   if (!Desc.isVariadic() &&

Modified: llvm/trunk/test/CodeGen/AMDGPU/uniform-cfg.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AMDGPU/uniform-cfg.ll?rev=269391&r1=269390&r2=269391&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/AMDGPU/uniform-cfg.ll (original)
+++ llvm/trunk/test/CodeGen/AMDGPU/uniform-cfg.ll Thu May 12 23:15:48 2016
@@ -226,7 +226,7 @@ ENDIF:
 ; SI: s_endpgm
 define void @icmp_users_different_blocks(i32 %cond, i32 addrspace(1)* %out) {
 bb:
-  %tmp = tail call i32 @llvm.r600.read.tidig.x() #0
+  %tmp = tail call i32 @llvm.amdgcn.workitem.id.x() #0
   %tmp1 = icmp sgt i32 %cond, 0
   br i1 %tmp1, label %bb2, label %bb9
 
@@ -279,7 +279,7 @@ done:
 ; SI: buffer_store_dword [[ONE]]
 define void @uniform_inside_divergent(i32 addrspace(1)* %out, i32 %cond) {
 entry:
-  %tid = call i32 @llvm.r600.read.tidig.x() #0
+  %tid = call i32 @llvm.amdgcn.workitem.id.x() #0
   %d_cmp = icmp ult i32 %tid, 16
   br i1 %d_cmp, label %if, label %endif
 
@@ -313,7 +313,7 @@ entry:
 
 if:
   store i32 0, i32 addrspace(1)* %out
-  %tid = call i32 @llvm.r600.read.tidig.x() #0
+  %tid = call i32 @llvm.amdgcn.workitem.id.x() #0
   %d_cmp = icmp ult i32 %tid, 16
   br i1 %d_cmp, label %if_uniform, label %endif
 
@@ -325,7 +325,7 @@ endif:
   ret void
 }
 
-; SI: {{^}}divergent_if_uniform_if:
+; SI-LABEL: {{^}}divergent_if_uniform_if:
 ; SI: v_cmp_eq_i32_e32 vcc, 0, v0
 ; SI: s_and_saveexec_b64 [[MASK:s\[[0-9]+:[0-9]+\]]], vcc
 ; SI: s_xor_b64 [[MASK:s\[[0-9]+:[0-9]+\]]], exec, [[MASK]]
@@ -340,7 +340,7 @@ endif:
 ; SI: s_endpgm
 define void @divergent_if_uniform_if(i32 addrspace(1)* %out, i32 %cond) {
 entry:
-  %tid = call i32 @llvm.r600.read.tidig.x() #0
+  %tid = call i32 @llvm.amdgcn.workitem.id.x() #0
   %d_cmp = icmp eq i32 %tid, 0
   br i1 %d_cmp, label %if, label %endif
 
@@ -360,6 +360,44 @@ exit:
   ret void
 }
 
-declare i32 @llvm.r600.read.tidig.x() #0
+; The condition of the branches in the two blocks are
+; uniform. MachineCSE replaces the 2nd condition with the inverse of
+; the first, leaving an scc use in a different block than it was
+; defed.
+
+; SI-LABEL: {{^}}cse_uniform_condition_different_blocks:
+; SI: s_load_dword [[COND:s[0-9]+]]
+; SI: s_cmp_lt_i32 [[COND]], 1
+; SI: s_cbranch_scc1 BB13_3
+
+; SI: BB#1:
+; SI-NOT: cmp
+; SI: buffer_load_dword
+; SI: buffer_store_dword
+; SI: s_cbranch_scc1 BB13_3
+
+; SI: BB13_3:
+; SI: s_endpgm
+define void @cse_uniform_condition_different_blocks(i32 %cond, i32 addrspace(1)* %out) {
+bb:
+  %tmp = tail call i32 @llvm.amdgcn.workitem.id.x() #0
+  %tmp1 = icmp sgt i32 %cond, 0
+  br i1 %tmp1, label %bb2, label %bb9
+
+bb2:                                              ; preds = %bb
+  %tmp3 = load volatile i32, i32 addrspace(1)* undef
+  store volatile i32 0, i32 addrspace(1)* undef
+  %tmp9 = icmp sle i32 %cond, 0
+  br i1 %tmp9, label %bb9, label %bb7
+
+bb7:                                              ; preds = %bb5
+  store i32 %tmp3, i32 addrspace(1)* %out
+  br label %bb9
+
+bb9:                                              ; preds = %bb8, %bb4
+  ret void
+}
+
+declare i32 @llvm.amdgcn.workitem.id.x() #0
 
 attributes #0 = { readnone }