[AMDGPU] Assert if stack grows downwards while lowering dynAlloca

[easyonaadit]

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[llvmbot]

@llvm/pr-subscribers-backend-amdgpu

Author: Aaditya (easyonaadit)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/119883.diff

2 Files Affected:

• (modified) llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp (+2-2)
• (modified) llvm/lib/Target/AMDGPU/SIISelLowering.cpp (+3-5)

diff --git a/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp b/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp
index e5baffc0f064b2..72c3e4a64c18bc 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp
@@ -1181,8 +1181,8 @@ bool AMDGPURegisterBankInfo::applyMappingDynStackAlloc(
 
   // Guard in case the stack growth direction ever changes with scratch
   // instructions.
-  if (TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown)
-    return false;
+  assert(TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsUp &&
+         "Stack grows upwards for AMDGPU\n");
 
   Register Dst = MI.getOperand(0).getReg();
   Register AllocSize = MI.getOperand(1).getReg();
diff --git a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
index 8dfebd36a962e1..9366cb31640f9b 100644
--- a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
@@ -4041,17 +4041,15 @@ SDValue SITargetLowering::lowerDYNAMIC_STACKALLOCImpl(SDValue Op,
   Chain = SP.getValue(1);
   MaybeAlign Alignment = cast<ConstantSDNode>(Tmp3)->getMaybeAlignValue();
   const TargetFrameLowering *TFL = Subtarget->getFrameLowering();
-  unsigned Opc =
-      TFL->getStackGrowthDirection() == TargetFrameLowering::StackGrowsUp
-          ? ISD::ADD
-          : ISD::SUB;
+  assert(TFL->getStackGrowthDirection() == TargetFrameLowering::StackGrowsUp &&
+         "Stack grows upwards for AMDGPU\n");
 
   SDValue ScaledSize = DAG.getNode(
       ISD::SHL, dl, VT, Size,
       DAG.getConstant(Subtarget->getWavefrontSizeLog2(), dl, MVT::i32));
 
   Align StackAlign = TFL->getStackAlign();
-  Tmp1 = DAG.getNode(Opc, dl, VT, SP, ScaledSize); // Value
+  Tmp1 = DAG.getNode(ISD::ADD, dl, VT, SP, ScaledSize); // Value
   if (Alignment && *Alignment > StackAlign) {
     Tmp1 = DAG.getNode(
         ISD::AND, dl, VT, Tmp1,