[llvm] [RISCV] Handle a split 2*XLen argument before pushing to PendingLocs. (PR #176183)

[Craig Topper via llvm-commits]

https://github.com/topperc created https://github.com/llvm/llvm-project/pull/176183

Previously we pushed the second part to PendingLocs first, but never used it since the all values were still in variables.

>From 4412213c1767fc30ec6f9347b546d6bf6387e04e Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Wed, 14 Jan 2026 23:54:45 -0800
Subject: [PATCH] [RISCV] Handle a split 2*XLen argument before pushing to
 PendingLocs.

Previously we pushed the second part to PendingLocs first, but
never used it since the all values were still in variables.
---
 llvm/lib/Target/RISCV/RISCVCallingConv.cpp | 32 +++++++++++-----------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/llvm/lib/Target/RISCV/RISCVCallingConv.cpp b/llvm/lib/Target/RISCV/RISCVCallingConv.cpp
index 78f47794a5b66..ede67bd9bc90a 100644
--- a/llvm/lib/Target/RISCV/RISCVCallingConv.cpp
+++ b/llvm/lib/Target/RISCV/RISCVCallingConv.cpp
@@ -510,25 +510,11 @@ bool llvm::CC_RISCV(unsigned ValNo, MVT ValVT, MVT LocVT,
     return false;
   }
 
-  // Split arguments might be passed indirectly, so keep track of the pending
-  // values. Split vectors are passed via a mix of registers and indirectly, so
-  // treat them as we would any other argument.
-  if (ValVT.isScalarInteger() && (ArgFlags.isSplit() || !PendingLocs.empty())) {
-    LocVT = XLenVT;
-    LocInfo = CCValAssign::Indirect;
-    PendingLocs.push_back(
-        CCValAssign::getPending(ValNo, ValVT, LocVT, LocInfo));
-    PendingArgFlags.push_back(ArgFlags);
-    if (!ArgFlags.isSplitEnd()) {
-      return false;
-    }
-  }
-
   // If the split argument only had two elements, it should be passed directly
   // in registers or on the stack.
   if (ValVT.isScalarInteger() && ArgFlags.isSplitEnd() &&
-      PendingLocs.size() <= 2) {
-    assert(PendingLocs.size() == 2 && "Unexpected PendingLocs.size()");
+      PendingLocs.size() <= 1) {
+    assert(PendingLocs.size() == 1 && "Unexpected PendingLocs.size()");
     // Apply the normal calling convention rules to the first half of the
     // split argument.
     CCValAssign VA = PendingLocs[0];
@@ -540,6 +526,20 @@ bool llvm::CC_RISCV(unsigned ValNo, MVT ValVT, MVT LocVT,
         ABI == RISCVABI::ABI_ILP32E || ABI == RISCVABI::ABI_LP64E);
   }
 
+  // Split arguments might be passed indirectly, so keep track of the pending
+  // values. Split vectors are passed via a mix of registers and indirectly, so
+  // treat them as we would any other argument.
+  if (ValVT.isScalarInteger() && (ArgFlags.isSplit() || !PendingLocs.empty())) {
+    LocVT = XLenVT;
+    LocInfo = CCValAssign::Indirect;
+    PendingLocs.push_back(
+        CCValAssign::getPending(ValNo, ValVT, LocVT, LocInfo));
+    PendingArgFlags.push_back(ArgFlags);
+    if (!ArgFlags.isSplitEnd()) {
+      return false;
+    }
+  }
+
   // Allocate to a register if possible, or else a stack slot.
   MCRegister Reg;
   unsigned StoreSizeBytes = XLen / 8;