AMDGPU: Don't assume call targets are registers

GlobalISel let through a call to null, which would then fold into the source operand like any other inline immediate. The SelectionDAG lowering deletes calls to null and undef as a workaround from before calls were supported. We should probably drop the special handling case in the DAG lowering now, since the middle end optimizers delete null calls anyway.
llvm · Jul 29, 2020 · 068808d · 068808d
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commit 068808d
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Showing 2 changed files with 32 additions and 23 deletions.
diff --git a/llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp b/llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp
@@ -963,26 +963,28 @@ bool SIInsertWaitcnts::generateWaitcntInstBefore(
 
       int CallAddrOpIdx =
           AMDGPU::getNamedOperandIdx(MI.getOpcode(), AMDGPU::OpName::src0);
-      RegInterval CallAddrOpInterval =
+
+      if (MI.getOperand(CallAddrOpIdx).isReg()) {
+        RegInterval CallAddrOpInterval =
           ScoreBrackets.getRegInterval(&MI, TII, MRI, TRI, CallAddrOpIdx);
 
-      for (int RegNo = CallAddrOpInterval.first;
-           RegNo < CallAddrOpInterval.second; ++RegNo)
-        ScoreBrackets.determineWait(
+        for (int RegNo = CallAddrOpInterval.first;
+             RegNo < CallAddrOpInterval.second; ++RegNo)
+          ScoreBrackets.determineWait(
             LGKM_CNT, ScoreBrackets.getRegScore(RegNo, LGKM_CNT), Wait);
 
-      int RtnAddrOpIdx =
-            AMDGPU::getNamedOperandIdx(MI.getOpcode(), AMDGPU::OpName::dst);
-      if (RtnAddrOpIdx != -1) {
-        RegInterval RtnAddrOpInterval =
+        int RtnAddrOpIdx =
+          AMDGPU::getNamedOperandIdx(MI.getOpcode(), AMDGPU::OpName::dst);
+        if (RtnAddrOpIdx != -1) {
+          RegInterval RtnAddrOpInterval =
             ScoreBrackets.getRegInterval(&MI, TII, MRI, TRI, RtnAddrOpIdx);
 
-        for (int RegNo = RtnAddrOpInterval.first;
-             RegNo < RtnAddrOpInterval.second; ++RegNo)
-          ScoreBrackets.determineWait(
+          for (int RegNo = RtnAddrOpInterval.first;
+               RegNo < RtnAddrOpInterval.second; ++RegNo)
+            ScoreBrackets.determineWait(
               LGKM_CNT, ScoreBrackets.getRegScore(RegNo, LGKM_CNT), Wait);
+        }
       }
-
     } else {
       // FIXME: Should not be relying on memoperands.
       // Look at the source operands of every instruction to see if

diff --git a/llvm/test/CodeGen/AMDGPU/call-constant.ll b/llvm/test/CodeGen/AMDGPU/call-constant.ll
@@ -1,11 +1,12 @@
-; RUN: llc -mtriple=amdgcn-amd-amdhsa < %s | FileCheck -check-prefix=GCN %s
+; RUN: llc -global-isel=0 -amdgpu-fixed-function-abi=0 -mtriple=amdgcn-amd-amdhsa < %s | FileCheck -check-prefixes=GCN,SDAG %s
+; RUN: llc -global-isel=1 -amdgpu-fixed-function-abi=1 -mtriple=amdgcn-amd-amdhsa < %s | FileCheck -check-prefixes=GCN,GISEL %s
 
 ; FIXME: Emitting unnecessary flat_scratch setup
 
 ; GCN-LABEL: {{^}}test_call_undef:
-; GCN: s_mov_b32 flat_scratch_lo, s5
-; GCN: s_add_u32 s4, s4, s7
-; GCN: s_lshr_b32
+; SDAG: s_mov_b32 flat_scratch_lo, s5
+; SDAG: s_add_u32 s4, s4, s7
+; SDAG: s_lshr_b32
 ; GCN: s_endpgm
 define amdgpu_kernel void @test_call_undef() #0 {
   %val = call i32 undef(i32 1)
@@ -15,17 +16,21 @@ define amdgpu_kernel void @test_call_undef() #0 {
 }
 
 ; GCN-LABEL: {{^}}test_tail_call_undef:
-; GCN: s_waitcnt
-; GCN-NEXT: .Lfunc_end
+; SDAG: s_waitcnt
+; SDAG-NEXT: .Lfunc_end
+
+; GISEL: s_swappc_b64 s{{\[[0-9]+:[0-9]+\]}}, s{{\[[0-9]+:[0-9]+\]}}
 define i32 @test_tail_call_undef() #0 {
   %call = tail call i32 undef(i32 1)
   ret i32 %call
 }
 
 ; GCN-LABEL: {{^}}test_call_null:
-; GCN: s_mov_b32 flat_scratch_lo, s5
-; GCN: s_add_u32 s4, s4, s7
-; GCN: s_lshr_b32
+; SDAG: s_mov_b32 flat_scratch_lo, s5
+; SDAG: s_add_u32 s4, s4, s7
+; SDAG: s_lshr_b32
+
+; GISEL: s_swappc_b64 s{{\[[0-9]+:[0-9]+\]}}, 0{{$}}
 ; GCN: s_endpgm
 define amdgpu_kernel void @test_call_null() #0 {
   %val = call i32 null(i32 1)
@@ -35,8 +40,10 @@ define amdgpu_kernel void @test_call_null() #0 {
 }
 
 ; GCN-LABEL: {{^}}test_tail_call_null:
-; GCN: s_waitcnt
-; GCN-NEXT: .Lfunc_end
+; SDAG: s_waitcnt
+; SDAG-NEXT: .Lfunc_end
+
+; GISEL: s_swappc_b64 s{{\[[0-9]+:[0-9]+\]}}, 0{{$}}
 define i32 @test_tail_call_null() #0 {
   %call = tail call i32 null(i32 1)
   ret i32 %call