AMDGPU/GlobalISel: Mark 1-bit integer constants as legal

[tstellar]

Summary

These are mostly legal, but will probably need special lowering for some
cases.

[arsenm]

LGTM

lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp

 
 #ifndef LLVM_BUILD_GLOBAL_ISEL
 #error "You shouldn't build this"
 #endif
 
 AMDGPULegalizerInfo::AMDGPULegalizerInfo() {
   using namespace TargetOpcode;
 
+  const LLT S1= LLT::scalar(1);
   const LLT S32 = LLT::scalar(32);
   const LLT S64 = LLT::scalar(64);
   const LLT P1 = LLT::pointer(1, 64);
   const LLT P2 = LLT::pointer(2, 64);
 
+  // FIXME: i1 operands to intrinsics should always be legal, but other i1
+  // values may not be legal.  We need to figure out how to distinguish
+  // between these two scenarios.
+  setAction({G_CONSTANT, S1}, Legal);
   setAction({G_CONSTANT, S32}, Legal);
   setAction({G_CONSTANT, S64}, Legal);
 
   setAction({G_FCONSTANT, S32}, Legal);
 
   setAction({G_GEP, P1}, Legal);
   setAction({G_GEP, P2}, Legal);
   setAction({G_GEP, 1, S64}, Legal);

test/CodeGen/AMDGPU/GlobalISel/legalize-constant.mir

 # RUN: llc -mtriple=amdgcn-mesa-mesa3d -mcpu=fiji -O0 -run-pass=legalizer -global-isel %s -o - | FileCheck %s
 
 --- |
   define void @test_constant() {
   entry:
     ret void
   }
 
   define void @test_fconstant() {
   entry:
     ret void
   }
+
+  declare void @llvm.amdgcn.exp.f32(i32, i32, float, float, float, float, i1, i1) #1
+
+  attributes #1 = { nounwind }
+
 ...
 
 ---
 name:            test_constant
 registers:
   - { id: 0, class: _ }
+  - { id: 1, class: _ }
 body: |
   bb.0.entry:
     ; CHECK-LABEL: name: test_constant
     ; CHECK: %0(s32) = G_CONSTANT i32 5
+    ; CHECK: %1(s1) = G_CONSTANT i1 false
 
     %0(s32) = G_CONSTANT i32 5
+    %1(s1) = G_CONSTANT i1 0
+    G_INTRINSIC_W_SIDE_EFFECTS intrinsic(@llvm.amdgcn.exp.f32), %0, %0, %0, %0, %0, %0, %1, %1;
 ...
 
 ---
 name:            test_fconstant
 registers:
   - { id: 0, class: _ }
   - { id: 1, class: _ }
 body: |
   bb.0.entry:
     ; CHECK-LABEL: name: test_fconstant
     ; CHECK: %0(s32) = G_FCONSTANT  float 1.000000e+00
     ; CHECK: %1(s32) = G_FCONSTANT  float 7.5
 
     %0(s32) = G_FCONSTANT float 1.0
     %1(s32) = G_FCONSTANT float 7.5
 ...