[RISCV][GISel] Make G_CONSTANT of pointers legal.

This is needed to support things like null pointers. Reviewed By: reames Differential Revision: https://reviews.llvm.org/D157822
llvm · Aug 14, 2023 · 1fa858d · 1fa858d
1 parent 700ca0e
commit 1fa858d
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Showing 3 changed files with 28 additions and 1 deletion.
diff --git a/llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp b/llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp
@@ -22,6 +22,7 @@ using namespace llvm;
 RISCVLegalizerInfo::RISCVLegalizerInfo(const RISCVSubtarget &ST) {
   const unsigned XLen = ST.getXLen();
   const LLT XLenLLT = LLT::scalar(XLen);
+  const LLT p0 = LLT::pointer(0, XLen);
 
   using namespace TargetOpcode;
 
@@ -81,7 +82,7 @@ RISCVLegalizerInfo::RISCVLegalizerInfo(const RISCVSubtarget &ST) {
   }
 
   getActionDefinitionsBuilder({G_CONSTANT, G_IMPLICIT_DEF})
-      .legalFor({XLenLLT})
+      .legalFor({XLenLLT, p0})
       .widenScalarToNextPow2(0)
       .clampScalar(0, XLenLLT, XLenLLT);
 

diff --git a/llvm/test/CodeGen/RISCV/GlobalISel/legalizer/rv32/legalize-const.mir b/llvm/test/CodeGen/RISCV/GlobalISel/legalizer/rv32/legalize-const.mir
@@ -111,3 +111,16 @@ body:             |
     PseudoRET implicit $x10, implicit $x11, implicit $x12
 
 ...
+---
+name:            const_null
+body:             |
+  bb.0.entry:
+    ; CHECK-LABEL: name: const_null
+    ; CHECK: [[C:%[0-9]+]]:_(p0) = G_CONSTANT i32 0
+    ; CHECK-NEXT: $x10 = COPY [[C]](p0)
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:_(p0) = G_CONSTANT i32 0
+    $x10 = COPY %0(p0)
+    PseudoRET implicit $x10
+
+...
diff --git a/llvm/test/CodeGen/RISCV/GlobalISel/legalizer/rv64/legalize-const.mir b/llvm/test/CodeGen/RISCV/GlobalISel/legalizer/rv64/legalize-const.mir
@@ -125,3 +125,16 @@ body:             |
     PseudoRET implicit $x10, implicit $x11, implicit $x12
 
 ...
+---
+name:            const_null
+body:             |
+  bb.0.entry:
+    ; CHECK-LABEL: name: const_null
+    ; CHECK: [[C:%[0-9]+]]:_(p0) = G_CONSTANT i64 0
+    ; CHECK-NEXT: $x10 = COPY [[C]](p0)
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:_(p0) = G_CONSTANT i64 0
+    $x10 = COPY %0(p0)
+    PseudoRET implicit $x10
+
+...