[gcc r12-7416] PR middle-end/80270: ICE in extract_bit_field_1

[Roger Sayle <sayle@gcc.gnu.org>]

https://gcc.gnu.org/g:7e5c6edeb1b2339e10f10bee270e61dbad985800

commit r12-7416-g7e5c6edeb1b2339e10f10bee270e61dbad985800
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Mon Feb 28 22:26:43 2022 +0000

    PR middle-end/80270: ICE in extract_bit_field_1
    
    This patch fixes PR middle-end/80270, an ICE-on-valid regression, where
    performing a bitfield extraction on a variable explicitly stored in a
    hard register by the user causes a segmentation fault during RTL
    expansion.  Nearly identical source code without the "asm" qualifier
    compiles fine.  The point of divergence is in simplify_gen_subreg
    which tries to avoid creating non-trivial SUBREGs of hard registers,
    to avoid problems during register allocation.  This suggests the
    simple solution proposed here, to copy hard registers to a new pseudo
    in extract_integral_bit_field, just before calling simplify_gen_subreg.
    
    2022-02-28  Roger Sayle  <roger@nextmovesoftware.com>
                Eric Botcazou  <ebotcazou@adacore.com>
    
    gcc/ChangeLog
            PR middle-end/80270
            * expmed.cc (extract_integral_bit_field): If OP0 is a hard
            register, copy it to a pseudo before calling simplify_gen_subreg.
    
    gcc/testsuite/ChangeLog
            * gcc.target/i386/pr80270.c: New test case.

Diff:
---
 gcc/expmed.cc                           |  4 ++++
 gcc/testsuite/gcc.target/i386/pr80270.c | 21 +++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/gcc/expmed.cc b/gcc/expmed.cc
index 80a16cedfd5..ed39c88bd04 100644
--- a/gcc/expmed.cc
+++ b/gcc/expmed.cc
@@ -1975,6 +1975,10 @@ extract_integral_bit_field (rtx op0, opt_scalar_int_mode op0_mode,
 					    unsignedp, reverse);
 	  return convert_extracted_bit_field (target, mode, tmode, unsignedp);
 	}
+      /* If OP0 is a hard register, copy it to a pseudo before calling
+	 simplify_gen_subreg.  */
+      if (REG_P (op0) && HARD_REGISTER_P (op0))
+	op0 = copy_to_reg (op0);
       op0 = simplify_gen_subreg (word_mode, op0, op0_mode.require (),
 				 bitnum / BITS_PER_WORD * UNITS_PER_WORD);
       op0_mode = word_mode;
diff --git a/gcc/testsuite/gcc.target/i386/pr80270.c b/gcc/testsuite/gcc.target/i386/pr80270.c
new file mode 100644
index 00000000000..89e9c33d090
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr80270.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse" } */
+
+typedef int v8 __attribute__((vector_size(8)));
+struct S1 {
+  v8 s1f;
+};
+struct S2 {
+  struct S1 s2f1;
+  v8 s2f2;
+};
+
+extern void foo(int);
+
+void bar() {
+  int tmp, i = 3;
+  register struct S2 b asm("xmm0");
+  tmp = b.s2f1.s1f[i];
+  foo(tmp);
+}
+