[Xtensa] Fix ConstantPool lowering for aggregate constants.

Author: andreisfr

llvm/lib/Target/Xtensa/XtensaInstrInfo.td

@@ -314,6 +314,13 @@ def : Pat<(i32 (extloadi16 addr_ish2:$addr)), (L16UI addr_ish2:$addr)>;
 def : Pat<(i32 (load (add i32:$s, (Xtensa_pcrel_wrapper tconstpool:$in)))),
           (L32I (ADD i32:$s, (L32R tconstpool:$in)), 0)>;
 
+// In some cases load from aggregate constant pattern maybe not matched.
+// It is assumed that load 4-byte constant pattern is already
+// applied, so this is the case of load from the aggregate constant.
+// We just load an address of aggregate constant.
+let AddedComplexity = -1 in
+def : Pat<(Xtensa_pcrel_wrapper tconstpool:$in), (L32R tconstpool:$in)>;
+
 //===----------------------------------------------------------------------===//
 // Conditional branch instructions
 //===----------------------------------------------------------------------===//

llvm/test/CodeGen/Xtensa/constantpool_aggregate.ll

@@ -0,0 +1,29 @@
+; RUN: llc -mtriple=xtensa -mattr=+fp -O1 -verify-machineinstrs < %s \
+; RUN:   | FileCheck %s
+
+define float @select_fp_consts(float %x) {
+; CHECK: .literal_position
+; CHECK-NEXT: .literal .LCPI0_0, 0
+; CHECK-NEXT: .literal .LCPI0_1, .LCP0_0
+; CHECK-LABEL: select_fp_consts:
+; CHECK: # %bb.0:                                # %entry
+; CHECK-NEXT: l32r	a8, .LCPI0_0
+; CHECK-NEXT: wfr	f8, a8
+; CHECK-NEXT: wfr	f9, a2
+; CHECK-NEXT: ule.s	b0, f9, f8
+; CHECK-NEXT: bf	b0, .LBB0_2
+; CHECK-NEXT: # %bb.1:                                # %entry
+; CHECK-NEXT: movi	a8, 0
+; CHECK-NEXT: j	.LBB0_3
+; CHECK-NEXT: .LBB0_2:
+; CHECK-NEXT: movi	a8, 4
+; CHECK-NEXT: .LBB0_3:                                # %entry
+; CHECK-NEXT: l32r	a9, .LCPI0_1
+; CHECK-NEXT: add	a8, a9, a8
+; CHECK-NEXT: l32i	a2, a8, 0
+; CHECK-NEXT: ret
+entry:
+  %c = fcmp ogt float %x, 0.000000e+00
+  %r = select i1 %c, float -1.000000e+00, float 1.000000e+00
+  ret float %r
+}