[llvm] [GISel][RISCV] Legalize shifts with non-trivial shamt types (PR #93019)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-globalisel

Author: Yingwei Zheng (dtcxzyw)

<details>
<summary>Changes</summary>

This patch widens the illegal shamt type `i48` -> `i64` to fix legalization failure: https://godbolt.org/z/4zMTnoW7h


---
Full diff: https://github.com/llvm/llvm-project/pull/93019.diff


2 Files Affected:

- (modified) llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp (+2-1) 
- (modified) llvm/test/CodeGen/RISCV/GlobalISel/legalizer/legalize-lshr-rv64.mir (+26) 


``````````diff
diff --git a/llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp b/llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp
index c73fe2c6cecbe..606569caada23 100644
--- a/llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp
+++ b/llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp
@@ -137,7 +137,8 @@ RISCVLegalizerInfo::RISCVLegalizerInfo(const RISCVSubtarget &ST)
       .widenScalarToNextPow2(0)
       .clampScalar(1, s32, sXLen)
       .clampScalar(0, s32, sXLen)
-      .minScalarSameAs(1, 0);
+      .minScalarSameAs(1, 0)
+      .widenScalarToNextPow2(1);
 
   auto &ExtActions =
       getActionDefinitionsBuilder({G_ZEXT, G_SEXT, G_ANYEXT})
diff --git a/llvm/test/CodeGen/RISCV/GlobalISel/legalizer/legalize-lshr-rv64.mir b/llvm/test/CodeGen/RISCV/GlobalISel/legalizer/legalize-lshr-rv64.mir
index 8cbae0fa0173e..43318118f09c5 100644
--- a/llvm/test/CodeGen/RISCV/GlobalISel/legalizer/legalize-lshr-rv64.mir
+++ b/llvm/test/CodeGen/RISCV/GlobalISel/legalizer/legalize-lshr-rv64.mir
@@ -336,3 +336,29 @@ body:             |
     PseudoRET implicit $x10
 
 ...
+---
+name:            lshr_i32_i48
+body:             |
+  bb.1:
+    liveins: $x10
+
+    ; CHECK-LABEL: name: lshr_i32_i48
+    ; CHECK: liveins: $x10
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s64) = COPY $x10
+    ; CHECK-NEXT: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 16
+    ; CHECK-NEXT: [[TRUNC:%[0-9]+]]:_(s32) = G_TRUNC [[COPY]](s64)
+    ; CHECK-NEXT: [[LSHR:%[0-9]+]]:_(s32) = G_LSHR [[TRUNC]], [[C]](s64)
+    ; CHECK-NEXT: [[ANYEXT:%[0-9]+]]:_(s64) = G_ANYEXT [[LSHR]](s32)
+    ; CHECK-NEXT: $x10 = COPY [[ANYEXT]](s64)
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %1:_(s64) = COPY $x10
+    %0:_(s48) = G_TRUNC %1(s64)
+    %2:_(s48) = G_CONSTANT i48 16
+    %6:_(s32) = G_TRUNC %0(s48)
+    %7:_(s32) = G_LSHR %6, %2(s48)
+    %5:_(s64) = G_ANYEXT %7(s32)
+    $x10 = COPY %5(s64)
+    PseudoRET implicit $x10
+
+...

``````````

</details>


https://github.com/llvm/llvm-project/pull/93019