GlobalISel: Constant fold integer min/max opcodes

[foad]

Looks obviously good.

[arsenm]

This was 930f2498d46305c7d787354fd629bd686fbcc3a3

llvm/lib/CodeGen/GlobalISel/CSEMIRBuilder.cpp

MachineInstrBuilder CSEMIRBuilder::buildInstr(unsigned Opc,
   case TargetOpcode::G_MUL:
   case TargetOpcode::G_OR:
   case TargetOpcode::G_SHL:
   case TargetOpcode::G_SUB:
   case TargetOpcode::G_XOR:
   case TargetOpcode::G_UDIV:
   case TargetOpcode::G_SDIV:
   case TargetOpcode::G_UREM:
-  case TargetOpcode::G_SREM: {
+  case TargetOpcode::G_SREM:
+  case TargetOpcode::G_SMIN:
+  case TargetOpcode::G_SMAX:
+  case TargetOpcode::G_UMIN:
+  case TargetOpcode::G_UMAX: {
     // Try to constant fold these.
     assert(SrcOps.size() == 2 && "Invalid sources");
     assert(DstOps.size() == 1 && "Invalid dsts");
     if (Optional<APInt> Cst = ConstantFoldBinOp(Opc, SrcOps[0].getReg(),
                                                 SrcOps[1].getReg(), *getMRI()))
       return buildConstant(DstOps[0], *Cst);
     break;
   }

llvm/lib/CodeGen/GlobalISel/Utils.cpp

Optional<APInt> llvm::ConstantFoldBinOp(unsigned Opcode, const Register Op1,
   case TargetOpcode::G_UREM:
     if (!C2.getBoolValue())
       break;
     return C1.urem(C2);
   case TargetOpcode::G_SREM:
     if (!C2.getBoolValue())
       break;
     return C1.srem(C2);
+  case TargetOpcode::G_SMIN:
+    return APIntOps::smin(C1, C2);
+  case TargetOpcode::G_SMAX:
+    return APIntOps::smax(C1, C2);
+  case TargetOpcode::G_UMIN:
+    return APIntOps::umin(C1, C2);
+  case TargetOpcode::G_UMAX:
+    return APIntOps::umax(C1, C2);
   }
 
   return None;
 }
 
 bool llvm::isKnownNeverNaN(Register Val, const MachineRegisterInfo &MRI,
                            bool SNaN) {
   const MachineInstr *DefMI = MRI.getVRegDef(Val);

llvm/test/CodeGen/AMDGPU/GlobalISel/combine-fold-binop-into-select.mir

bb.0:
     liveins: $vgpr0
     ; CHECK-LABEL: name: fold_smin_into_select_s32_0
     ; CHECK: liveins: $vgpr0
     ; CHECK: %reg:_(s32) = COPY $vgpr0
     ; CHECK: %zero:_(s32) = G_CONSTANT i32 0
     ; CHECK: %cond:_(s1) = G_ICMP intpred(eq), %reg(s32), %zero
     ; CHECK: %ten:_(s32) = G_CONSTANT i32 10
     ; CHECK: %twenty:_(s32) = G_CONSTANT i32 20
-    ; CHECK: %thirty:_(s32) = G_CONSTANT i32 30
-    ; CHECK: [[SMIN:%[0-9]+]]:_(s32) = G_SMIN %ten, %thirty
-    ; CHECK: [[SMIN1:%[0-9]+]]:_(s32) = G_SMIN %twenty, %thirty
-    ; CHECK: %smin:_(s32) = G_SELECT %cond(s1), [[SMIN]], [[SMIN1]]
+    ; CHECK: %smin:_(s32) = G_SELECT %cond(s1), %ten, %twenty
     ; CHECK: S_ENDPGM 0, implicit %smin(s32)
     %reg:_(s32) = COPY $vgpr0
     %zero:_(s32) = G_CONSTANT i32 0
     %cond:_(s1) = G_ICMP intpred(eq), %reg, %zero
     %ten:_(s32) = G_CONSTANT i32 10
     %twenty:_(s32) = G_CONSTANT i32 20
     %select:_(s32) = G_SELECT %cond, %ten, %twenty
     %thirty:_(s32) = G_CONSTANT i32 30
     %smin:_(s32) = G_SMIN %select, %thirty
     S_ENDPGM 0, implicit %smin
 ...
 
 ---
 name: fold_smax_into_select_s32_0
 tracksRegLiveness: true
 body: |
   bb.0:
     liveins: $vgpr0
     ; CHECK-LABEL: name: fold_smax_into_select_s32_0
     ; CHECK: liveins: $vgpr0
-    ; CHECK: %reg:_(s32) = COPY $vgpr0
-    ; CHECK: %zero:_(s32) = G_CONSTANT i32 0
-    ; CHECK: %cond:_(s1) = G_ICMP intpred(eq), %reg(s32), %zero
-    ; CHECK: %ten:_(s32) = G_CONSTANT i32 10
-    ; CHECK: %twenty:_(s32) = G_CONSTANT i32 20
     ; CHECK: %thirty:_(s32) = G_CONSTANT i32 30
-    ; CHECK: [[SMAX:%[0-9]+]]:_(s32) = G_SMAX %ten, %thirty
-    ; CHECK: [[SMAX1:%[0-9]+]]:_(s32) = G_SMAX %twenty, %thirty
-    ; CHECK: %smax:_(s32) = G_SELECT %cond(s1), [[SMAX]], [[SMAX1]]
-    ; CHECK: S_ENDPGM 0, implicit %smax(s32)
+    ; CHECK: S_ENDPGM 0, implicit %thirty(s32)
     %reg:_(s32) = COPY $vgpr0
     %zero:_(s32) = G_CONSTANT i32 0
     %cond:_(s1) = G_ICMP intpred(eq), %reg, %zero
     %ten:_(s32) = G_CONSTANT i32 10
     %twenty:_(s32) = G_CONSTANT i32 20
     %select:_(s32) = G_SELECT %cond, %ten, %twenty
     %thirty:_(s32) = G_CONSTANT i32 30
     %smax:_(s32) = G_SMAX %select, %thirty
     S_ENDPGM 0, implicit %smax
 ...
 
 ---
 name: fold_umin_into_select_s32_0
 tracksRegLiveness: true
 body: |
   bb.0:
     liveins: $vgpr0
     ; CHECK-LABEL: name: fold_umin_into_select_s32_0
     ; CHECK: liveins: $vgpr0
     ; CHECK: %reg:_(s32) = COPY $vgpr0
     ; CHECK: %zero:_(s32) = G_CONSTANT i32 0
     ; CHECK: %cond:_(s1) = G_ICMP intpred(eq), %reg(s32), %zero
     ; CHECK: %ten:_(s32) = G_CONSTANT i32 10
     ; CHECK: %twenty:_(s32) = G_CONSTANT i32 20
-    ; CHECK: %thirty:_(s32) = G_CONSTANT i32 30
-    ; CHECK: [[UMIN:%[0-9]+]]:_(s32) = G_UMIN %ten, %thirty
-    ; CHECK: [[UMIN1:%[0-9]+]]:_(s32) = G_UMIN %twenty, %thirty
-    ; CHECK: %umin:_(s32) = G_SELECT %cond(s1), [[UMIN]], [[UMIN1]]
+    ; CHECK: %umin:_(s32) = G_SELECT %cond(s1), %ten, %twenty
     ; CHECK: S_ENDPGM 0, implicit %umin(s32)
     %reg:_(s32) = COPY $vgpr0
     %zero:_(s32) = G_CONSTANT i32 0
     %cond:_(s1) = G_ICMP intpred(eq), %reg, %zero
     %ten:_(s32) = G_CONSTANT i32 10
     %twenty:_(s32) = G_CONSTANT i32 20
     %select:_(s32) = G_SELECT %cond, %ten, %twenty
     %thirty:_(s32) = G_CONSTANT i32 30
     %umin:_(s32) = G_UMIN %select, %thirty
     S_ENDPGM 0, implicit %umin
 ...
 
 ---
 name: fold_umax_into_select_s32_0
 tracksRegLiveness: true
 body: |
   bb.0:
     liveins: $vgpr0
     ; CHECK-LABEL: name: fold_umax_into_select_s32_0
     ; CHECK: liveins: $vgpr0
-    ; CHECK: %reg:_(s32) = COPY $vgpr0
-    ; CHECK: %zero:_(s32) = G_CONSTANT i32 0
-    ; CHECK: %cond:_(s1) = G_ICMP intpred(eq), %reg(s32), %zero
-    ; CHECK: %ten:_(s32) = G_CONSTANT i32 10
-    ; CHECK: %twenty:_(s32) = G_CONSTANT i32 20
     ; CHECK: %thirty:_(s32) = G_CONSTANT i32 30
-    ; CHECK: [[UMAX:%[0-9]+]]:_(s32) = G_UMAX %ten, %thirty
-    ; CHECK: [[UMAX1:%[0-9]+]]:_(s32) = G_UMAX %twenty, %thirty
-    ; CHECK: %umax:_(s32) = G_SELECT %cond(s1), [[UMAX]], [[UMAX1]]
-    ; CHECK: S_ENDPGM 0, implicit %umax(s32)
+    ; CHECK: S_ENDPGM 0, implicit %thirty(s32)
     %reg:_(s32) = COPY $vgpr0
     %zero:_(s32) = G_CONSTANT i32 0
     %cond:_(s1) = G_ICMP intpred(eq), %reg, %zero
     %ten:_(s32) = G_CONSTANT i32 10
     %twenty:_(s32) = G_CONSTANT i32 20
     %select:_(s32) = G_SELECT %cond, %ten, %twenty
     %thirty:_(s32) = G_CONSTANT i32 30
     %umax:_(s32) = G_UMAX %select, %thirty