This reverts commit r17-684-gfed7299b89f62b.

The "%" modifier does not work for hard-reg constraints.
See https://gcc.gnu.org/pipermail/gcc-patches/2026-May/718682.html

Signed-off-by: Dimitar Dimitrov <[email protected]>
---
 gcc/config/pru/constraints.md | 14 ++++++++++++++
 gcc/config/pru/predicates.md  |  9 ++++++---
 gcc/config/pru/pru.h          | 18 +++++++++++++++++-
 gcc/config/pru/pru.md         | 14 +++++++-------
 4 files changed, 44 insertions(+), 11 deletions(-)

diff --git a/gcc/config/pru/constraints.md b/gcc/config/pru/constraints.md
index f93d2d8f326..265a3c8f91e 100644
--- a/gcc/config/pru/constraints.md
+++ b/gcc/config/pru/constraints.md
@@ -32,6 +32,7 @@
 ;;  m: Memory operand.
 ;;
 ;; The following constraints are intended for internal use only:
+;;  Rmd0, Rms0, Rms1: Registers for MUL instruction operands.
 ;;  Rsib: Jump address register suitable for sibling calls.
 ;;  Rrio: The R30 and R31 I/O registers.
 ;;  M: -255 to 0 (for converting ADD to SUB with suitable UBYTE OP2).
@@ -50,6 +51,19 @@ (define_register_constraint "Rsib" "SIB_REGS"
   "@internal
   A register suitable for an indirect sibcall.")
 
+(define_register_constraint "Rmd0" "MULDST_REGS"
+  "@internal
+  The multiply destination register."
+  "regno == MULDST_REGNUM")
+
+(define_register_constraint "Rms0" "MULSRC0_REGS"
+  "@internal
+  The multiply source 0 register.")
+
+(define_register_constraint "Rms1" "MULSRC1_REGS"
+  "@internal
+  The multiply source 1 register.")
+
 (define_register_constraint "Rrio" "REGIO_REGS"
   "@internal
   The R30 and R31 I/O registers.")
diff --git a/gcc/config/pru/predicates.md b/gcc/config/pru/predicates.md
index baff4aa7e8f..4d8c447568b 100644
--- a/gcc/config/pru/predicates.md
+++ b/gcc/config/pru/predicates.md
@@ -83,7 +83,8 @@ (define_predicate "pru_muldst_operand"
       else
        return 0;
 
-      return regno == MULDST_REGNUM || regno >= FIRST_PSEUDO_REGISTER;
+      return REGNO_REG_CLASS (regno) == MULDST_REGS
+            || regno >= FIRST_PSEUDO_REGISTER;
     }
   return 0;
 })
@@ -102,7 +103,8 @@ (define_predicate "pru_mulsrc0_operand"
       else
        return 0;
 
-      return regno == MULSRC0_REGNUM || regno >= FIRST_PSEUDO_REGISTER;
+      return REGNO_REG_CLASS (regno) == MULSRC0_REGS
+            || regno >= FIRST_PSEUDO_REGISTER;
     }
   return 0;
 })
@@ -121,7 +123,8 @@ (define_predicate "pru_mulsrc1_operand"
       else
        return 0;
 
-      return regno == MULSRC1_REGNUM || regno >= FIRST_PSEUDO_REGISTER;
+      return REGNO_REG_CLASS (regno) == MULSRC1_REGS
+            || regno >= FIRST_PSEUDO_REGISTER;
     }
   return 0;
 })
diff --git a/gcc/config/pru/pru.h b/gcc/config/pru/pru.h
index 3737a43e869..a370d08c385 100644
--- a/gcc/config/pru/pru.h
+++ b/gcc/config/pru/pru.h
@@ -216,6 +216,10 @@ enum reg_class
 {
   NO_REGS,
   SIB_REGS,
+  LOOPCNTR_REGS,
+  MULDST_REGS,
+  MULSRC0_REGS,
+  MULSRC1_REGS,
   REGIO_REGS,
   GP_REGS,
   ALL_REGS,
@@ -227,6 +231,10 @@ enum reg_class
 #define REG_CLASS_NAMES   \
   {  "NO_REGS",                  \
      "SIB_REGS",         \
+     "LOOPCNTR_REGS",    \
+     "MULDST_REGS",      \
+     "MULSRC0_REGS",     \
+     "MULSRC1_REGS",     \
      "REGIO_REGS",       \
      "GP_REGS",                  \
      "ALL_REGS" }
@@ -237,6 +245,10 @@ enum reg_class
   {                                                            \
     /* NO_REGS       */ { 0, 0, 0, 0, 0},                      \
     /* SIB_REGS              */ { 0xf, 0xff000000u, ~0u, 0xffffffu, 0},\
+    /* LOOPCNTR_REGS  */ { 0, 0, 0, 0, 0xf},                   \
+    /* MULDST_REGS    */ { 0, 0, 0, 0x0000ff00u, 0},           \
+    /* MULSRC0_REGS   */ { 0, 0, 0, 0x000f0000u, 0},           \
+    /* MULSRC1_REGS   */ { 0, 0, 0, 0x00f00000u, 0},           \
     /* REGIO_REGS     */ { 0, 0, 0, 0xff000000u, 0},           \
     /* GP_REGS       */ { ~0u, ~0u, ~0u, ~0u, 0},              \
     /* ALL_REGS              */ { ~0u, ~0u, ~0u, ~0u, ~0u}             \
@@ -245,11 +257,15 @@ enum reg_class
 
 #define GP_REG_P(REGNO) ((unsigned)(REGNO) <= LAST_GP_REGNUM)
 #define REGNO_REG_CLASS(REGNO)                                             \
-       ((REGNO) == R30_REGNUM ? REGIO_REGS                                 \
+       ((REGNO) == MULDST_REGNUM ? MULDST_REGS                             \
+        : (REGNO) == MULSRC0_REGNUM ? MULSRC0_REGS                         \
+        : (REGNO) == MULSRC1_REGNUM ? MULSRC1_REGS                         \
+        : (REGNO) == R30_REGNUM ? REGIO_REGS                               \
         : (REGNO) == R31_REGNUM ? REGIO_REGS                               \
         : (REGNO) >= FIRST_ARG_REGNUM                                      \
            && (REGNO) <= LAST_ARG_REGNUM ? SIB_REGS                        \
         : (REGNO) == STATIC_CHAIN_REGNUM ? SIB_REGS                        \
+        : (REGNO) == LOOPCNTR_REGNUM ? LOOPCNTR_REGS                       \
         : (REGNO) <= LAST_NONIO_GP_REGNUM ? GP_REGS                        \
         : ALL_REGS)
 
diff --git a/gcc/config/pru/pru.md b/gcc/config/pru/pru.md
index 50ef65fc512..93638963d29 100644
--- a/gcc/config/pru/pru.md
+++ b/gcc/config/pru/pru.md
@@ -1208,26 +1208,26 @@ (define_insn "one_cmpldi2"
   [(set_attr "type" "alu")
    (set_attr "length" "8")])
 
-;; Multiply instruction.  The nop is required to ensure that source
+;; Multiply instruction.  The nop is required to ensure that Rmd0 and Rms0
 ;; registers are sampled and multiplication is executed on those values.
 ;; Only after that one cycle can xin obtain the result.
 
 (define_insn "mulsi3"
-  [(set (match_operand:SI 0 "pru_muldst_operand"          "={r26}")
-       (mult:SI (match_operand:SI 1 "pru_mulsrc0_operand" "%{r28}")
-                (match_operand:SI 2 "pru_mulsrc1_operand" "{r29}")))]
+  [(set (match_operand:SI 0 "pru_muldst_operand"          "=Rmd0")
+       (mult:SI (match_operand:SI 1 "pru_mulsrc0_operand" "%Rms0")
+                (match_operand:SI 2 "pru_mulsrc1_operand" "Rms1")))]
   "TARGET_OPT_MUL"
   "nop\;xin\\t0, %0, 4"
   [(set_attr "type" "alu")
    (set_attr "length" "8")])
 
 (define_insn "umulsidi3"
-  [(set (match_operand:DI 0 "pru_muldst_operand"          "={r26}")
+  [(set (match_operand:DI 0 "pru_muldst_operand"          "=Rmd0")
        (mult:DI
          (zero_extend:DI
-           (match_operand:SI 1 "pru_mulsrc0_operand"      "%{r28}"))
+           (match_operand:SI 1 "pru_mulsrc0_operand"      "%Rms0"))
          (zero_extend:DI
-           (match_operand:SI 2 "pru_mulsrc1_operand"      "{r29}"))))]
+           (match_operand:SI 2 "pru_mulsrc1_operand"      "Rms1"))))]
   "TARGET_OPT_MUL"
   "nop\;xin\\t0, %0, 8"
   [(set_attr "type" "alu")
-- 
2.54.0

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