[llvm] [LoongArch][ISel] Check the number of sign bits in `PatGprGpr_32` (PR #107432)

Thu Sep 5 10:02:22 PDT 2024

llvmbot wrote:




@llvm/pr-subscribers-backend-loongarch

Author: Yingwei Zheng (dtcxzyw)

<details>
<summary>Changes</summary>

After https://github.com/llvm/llvm-project/pull/92205, LoongArch ISel selects `div.w` for `trunc i64 (sdiv i64 3202030857, (sext i32 X to i64)) to i32`. It is incorrect since `3202030857` is not a signed 32-bit constant. It will produce wrong result when `X == 2`: https://alive2.llvm.org/ce/z/pzfGZZ

This patch adds additional `sexti32` checks to operands of `PatGprGpr_32`.
Alive2 proof: https://alive2.llvm.org/ce/z/AkH5Mp

Fix #107414.


---
Full diff: https://github.com/llvm/llvm-project/pull/107432.diff


2 Files Affected:

- (modified) llvm/lib/Target/LoongArch/LoongArchInstrInfo.td (+4-4) 
- (modified) llvm/test/CodeGen/LoongArch/ir-instruction/sdiv-udiv-srem-urem.ll (+61-4) 


``````````diff

diff --git a/llvm/lib/Target/LoongArch/LoongArchInstrInfo.td b/llvm/lib/Target/LoongArch/LoongArchInstrInfo.td
index 0ab429817724c4..92263cc6b779b7 100644
--- a/llvm/lib/Target/LoongArch/LoongArchInstrInfo.td
+++ b/llvm/lib/Target/LoongArch/LoongArchInstrInfo.td
@@ -1065,10 +1065,13 @@ def RDTIME_D : RDTIME_2R<0x00006800>;
 
 /// Generic pattern classes
 
+def sexti32 : ComplexPattern<i64, 1, "selectSExti32">;
+def zexti32 : ComplexPattern<i64, 1, "selectZExti32">;
+
 class PatGprGpr<SDPatternOperator OpNode, LAInst Inst>
     : Pat<(OpNode GPR:$rj, GPR:$rk), (Inst GPR:$rj, GPR:$rk)>;
 class PatGprGpr_32<SDPatternOperator OpNode, LAInst Inst>
-    : Pat<(sext_inreg (OpNode GPR:$rj, GPR:$rk), i32), (Inst GPR:$rj, GPR:$rk)>;
+    : Pat<(sext_inreg (OpNode (sexti32 GPR:$rj), (sexti32 GPR:$rk)), i32), (Inst GPR:$rj, GPR:$rk)>;
 class PatGpr<SDPatternOperator OpNode, LAInst Inst>
     : Pat<(OpNode GPR:$rj), (Inst GPR:$rj)>;
 
@@ -1095,9 +1098,6 @@ def shiftMaskGRLen
     : ComplexPattern<GRLenVT, 1, "selectShiftMaskGRLen", [], [], 0>;
 def shiftMask32 : ComplexPattern<i64, 1, "selectShiftMask32", [], [], 0>;
 
-def sexti32 : ComplexPattern<i64, 1, "selectSExti32">;
-def zexti32 : ComplexPattern<i64, 1, "selectZExti32">;
-
 class shiftop<SDPatternOperator operator>
     : PatFrag<(ops node:$val, node:$count),
               (operator node:$val, (GRLenVT (shiftMaskGRLen node:$count)))>;
diff --git a/llvm/test/CodeGen/LoongArch/ir-instruction/sdiv-udiv-srem-urem.ll b/llvm/test/CodeGen/LoongArch/ir-instruction/sdiv-udiv-srem-urem.ll
index ab3eec240db3c1..8c2f67896efc46 100644
--- a/llvm/test/CodeGen/LoongArch/ir-instruction/sdiv-udiv-srem-urem.ll
+++ b/llvm/test/CodeGen/LoongArch/ir-instruction/sdiv-udiv-srem-urem.ll
@@ -189,8 +189,6 @@ define signext i32 @sdiv_si32_ui32_ui32(i32 %a, i32 %b) {
 ;
 ; LA64-LABEL: sdiv_si32_ui32_ui32:
 ; LA64:       # %bb.0: # %entry
-; LA64-NEXT:    addi.w $a1, $a1, 0
-; LA64-NEXT:    addi.w $a0, $a0, 0
 ; LA64-NEXT:    div.w $a0, $a0, $a1
 ; LA64-NEXT:    ret
 ;
@@ -205,8 +203,6 @@ define signext i32 @sdiv_si32_ui32_ui32(i32 %a, i32 %b) {
 ;
 ; LA64-TRAP-LABEL: sdiv_si32_ui32_ui32:
 ; LA64-TRAP:       # %bb.0: # %entry
-; LA64-TRAP-NEXT:    addi.w $a1, $a1, 0
-; LA64-TRAP-NEXT:    addi.w $a0, $a0, 0
 ; LA64-TRAP-NEXT:    div.w $a0, $a0, $a1
 ; LA64-TRAP-NEXT:    bnez $a1, .LBB5_2
 ; LA64-TRAP-NEXT:  # %bb.1: # %entry
@@ -1151,3 +1147,64 @@ entry:
   %r = urem i64 %a, %b
   ret i64 %r
 }
+
+define signext i32 @pr107414(i32 signext %x) {
+; LA32-LABEL: pr107414:
+; LA32:       # %bb.0: # %entry
+; LA32-NEXT:    addi.w $sp, $sp, -16
+; LA32-NEXT:    .cfi_def_cfa_offset 16
+; LA32-NEXT:    st.w $ra, $sp, 12 # 4-byte Folded Spill
+; LA32-NEXT:    .cfi_offset 1, -4
+; LA32-NEXT:    move $a2, $a0
+; LA32-NEXT:    srai.w $a3, $a0, 31
+; LA32-NEXT:    lu12i.w $a0, -266831
+; LA32-NEXT:    ori $a0, $a0, 3337
+; LA32-NEXT:    move $a1, $zero
+; LA32-NEXT:    bl %plt(__divdi3)
+; LA32-NEXT:    ld.w $ra, $sp, 12 # 4-byte Folded Reload
+; LA32-NEXT:    addi.w $sp, $sp, 16
+; LA32-NEXT:    ret
+;
+; LA64-LABEL: pr107414:
+; LA64:       # %bb.0: # %entry
+; LA64-NEXT:    lu12i.w $a1, -266831
+; LA64-NEXT:    ori $a1, $a1, 3337
+; LA64-NEXT:    lu32i.d $a1, 0
+; LA64-NEXT:    div.d $a0, $a1, $a0
+; LA64-NEXT:    addi.w $a0, $a0, 0
+; LA64-NEXT:    ret
+;
+; LA32-TRAP-LABEL: pr107414:
+; LA32-TRAP:       # %bb.0: # %entry
+; LA32-TRAP-NEXT:    addi.w $sp, $sp, -16
+; LA32-TRAP-NEXT:    .cfi_def_cfa_offset 16
+; LA32-TRAP-NEXT:    st.w $ra, $sp, 12 # 4-byte Folded Spill
+; LA32-TRAP-NEXT:    .cfi_offset 1, -4
+; LA32-TRAP-NEXT:    move $a2, $a0
+; LA32-TRAP-NEXT:    srai.w $a3, $a0, 31
+; LA32-TRAP-NEXT:    lu12i.w $a0, -266831
+; LA32-TRAP-NEXT:    ori $a0, $a0, 3337
+; LA32-TRAP-NEXT:    move $a1, $zero
+; LA32-TRAP-NEXT:    bl %plt(__divdi3)
+; LA32-TRAP-NEXT:    ld.w $ra, $sp, 12 # 4-byte Folded Reload
+; LA32-TRAP-NEXT:    addi.w $sp, $sp, 16
+; LA32-TRAP-NEXT:    ret
+;
+; LA64-TRAP-LABEL: pr107414:
+; LA64-TRAP:       # %bb.0: # %entry
+; LA64-TRAP-NEXT:    lu12i.w $a1, -266831
+; LA64-TRAP-NEXT:    ori $a1, $a1, 3337
+; LA64-TRAP-NEXT:    lu32i.d $a1, 0
+; LA64-TRAP-NEXT:    div.d $a1, $a1, $a0
+; LA64-TRAP-NEXT:    bnez $a0, .LBB32_2
+; LA64-TRAP-NEXT:  # %bb.1: # %entry
+; LA64-TRAP-NEXT:    break 7
+; LA64-TRAP-NEXT:  .LBB32_2: # %entry
+; LA64-TRAP-NEXT:    addi.w $a0, $a1, 0
+; LA64-TRAP-NEXT:    ret
+entry:
+  %conv = sext i32 %x to i64
+  %div = sdiv i64 3202030857, %conv
+  %conv1 = trunc i64 %div to i32
+  ret i32 %conv1
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/107432
