diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 176a1372e66..f2021d2c51a 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,13 @@
+2008-01-30  Richard Sandiford  <rsandifo@nildram.co.uk>
+
+	PR rtl-optimization/34998
+	* global.c (build_insn_chain): Treat non-subreg_lowpart
+	SUBREGs of pseudos as clobbering all the words covered by the
+	SUBREG, not just all the bytes.
+	* ra-conflict.c (clear_reg_in_live): Likewise.  Take the
+	original df_ref rather than an extract parameter.
+	(global_conflicts): Update call accordingly.
+
 2008-01-30  Andreas Krebbel  <krebbel1@de.ibm.com>
 
 	* config/s390/fixdfdi.h (__fixunstfdi, __fixtfdi): Rearrange
diff --git a/gcc/global.c b/gcc/global.c
index b8a0ec78158..12641a60cba 100644
--- a/gcc/global.c
+++ b/gcc/global.c
@@ -1501,6 +1501,17 @@ build_insn_chain (void)
 						  live_subregs, 
 						  live_subregs_used,
 						  regno, reg);
+
+			    if (!DF_REF_FLAGS_IS_SET
+				(def, DF_REF_STRICT_LOWER_PART))
+			      {
+				/* Expand the range to cover entire words.
+				   Bytes added here are "don't care".  */
+				start = start / UNITS_PER_WORD * UNITS_PER_WORD;
+				last = ((last + UNITS_PER_WORD - 1)
+					/ UNITS_PER_WORD * UNITS_PER_WORD);
+			      }
+
 			    /* Ignore the paradoxical bits.  */
 			    if ((int)last > live_subregs_used[regno])
 			      last = live_subregs_used[regno];
diff --git a/gcc/ra-conflict.c b/gcc/ra-conflict.c
index ce1dfdfcfb7..78d4f9246f0 100644
--- a/gcc/ra-conflict.c
+++ b/gcc/ra-conflict.c
@@ -441,16 +441,14 @@ ra_init_live_subregs (bool init_value,
 
 
 /* Set REG to be not live in the sets ALLOCNOS_LIVE, LIVE_SUBREGS,
-   HARD_REGS_LIVE.  If EXTRACT is false, assume that the entire reg is
-   set not live even if REG is a subreg.  */
+   HARD_REGS_LIVE.  DEF is the definition of the register.  */
 
 inline static void
 clear_reg_in_live (sparseset allocnos_live,
 		   sbitmap *live_subregs, 
 		   int *live_subregs_used,
 		   HARD_REG_SET *hard_regs_live, 
-		   rtx reg,
-		   bool extract)
+		   rtx reg, struct df_ref *def)
 {
   unsigned int regno = (GET_CODE (reg) == SUBREG) 
     ? REGNO (SUBREG_REG (reg)): REGNO (reg);
@@ -458,8 +456,8 @@ clear_reg_in_live (sparseset allocnos_live,
 
   if (allocnum >= 0)
     {
-      if ((GET_CODE (reg) == SUBREG) && !extract)
-
+      if (GET_CODE (reg) == SUBREG
+	  && !DF_REF_FLAGS_IS_SET (def, DF_REF_EXTRACT))
 	{
 	  unsigned int start = SUBREG_BYTE (reg);
 	  unsigned int last = start + GET_MODE_SIZE (GET_MODE (reg));
@@ -467,6 +465,15 @@ clear_reg_in_live (sparseset allocnos_live,
 	  ra_init_live_subregs (sparseset_bit_p (allocnos_live, allocnum), 
 				live_subregs, live_subregs_used, allocnum, reg);
 
+	  if (!DF_REF_FLAGS_IS_SET (def, DF_REF_STRICT_LOWER_PART))
+	    {
+	      /* Expand the range to cover entire words.
+		 Bytes added here are "don't care".  */
+	      start = start / UNITS_PER_WORD * UNITS_PER_WORD;
+	      last = ((last + UNITS_PER_WORD - 1)
+		      / UNITS_PER_WORD * UNITS_PER_WORD);
+	    }
+
 	  /* Ignore the paradoxical bits.  */
 	  if ((int)last > live_subregs_used[allocnum])
 	    last = live_subregs_used[allocnum];
@@ -503,7 +510,8 @@ clear_reg_in_live (sparseset allocnos_live,
   if (! fixed_regs[regno])
     {
       unsigned int start = regno;
-      if ((GET_CODE (reg) == SUBREG) && !extract)
+      if (GET_CODE (reg) == SUBREG
+	  && !DF_REF_FLAGS_IS_SET (def, DF_REF_EXTRACT))
 	{
 	  unsigned int last;
 	  start += SUBREG_BYTE (reg);
@@ -890,8 +898,7 @@ global_conflicts (void)
 		  rtx reg = DF_REF_REG (def);
 
 		  clear_reg_in_live (allocnos_live, live_subregs, live_subregs_used,
-				     &hard_regs_live, reg,
-				     DF_REF_FLAGS_IS_SET (def, DF_REF_EXTRACT));
+				     &hard_regs_live, reg, def);
 		  if (dump_file)
 		    dump_ref (dump_file, "  clearing def", "\n", 
 			      reg, DF_REF_REGNO (def), live_subregs, live_subregs_used);