[RISCV] Properly support RISCVISD::LLA in getTargetConstantFromLoad.

We need to pass the operand of LLA to GetSupportedConstantPool.

This replaces llvm#142292 with test from there added as a pre-commit
for both medlow and pic.

Author: topperc

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -21062,7 +21062,7 @@ RISCVTargetLowering::getTargetConstantFromLoad(LoadSDNode *Ld) const {
 
   // Simple case, LLA.
   if (Ptr.getOpcode() == RISCVISD::LLA) {
-    auto *CNode = GetSupportedConstantPool(Ptr);
+    auto *CNode = GetSupportedConstantPool(Ptr.getOperand(0));
     if (!CNode || CNode->getTargetFlags() != 0)
       return nullptr;
 

llvm/test/CodeGen/RISCV/constpool-known-bits.ll

@@ -35,7 +35,7 @@ define i64 @test(i32 noundef signext %c, i32 noundef signext %d) {
 ; PIC-NEXT:    addi a0, a0, %pcrel_lo(.Lpcrel_hi0)
 ; PIC-NEXT:    ld a0, 0(a0)
 ; PIC-NEXT:    mul a0, a1, a0
-; PIC-NEXT:    ori a0, a0, 127
+; PIC-NEXT:    addi a0, a0, 127
 ; PIC-NEXT:    mul a0, a1, a0
 ; PIC-NEXT:  .Lpcrel_hi1:
 ; PIC-NEXT:    auipc a2, %pcrel_hi(.LCPI0_1)