diff --git a/ChangeLog.txt b/ChangeLog.txt
index c8b554b0..69e1262a 100644
--- a/ChangeLog.txt
+++ b/ChangeLog.txt
@@ -11,6 +11,16 @@ incorrectly encode certain JPEG images when quality=100 and the fast integer
 forward DCT were used.  This was known to cause 'make test' to fail when the
 library was built with '-march=haswell' on x86 systems.
 
+[3] Fixed an issue whereby libjpeg-turbo would crash when built with the latest
+& greatest development version of the Clang/LLVM compiler.  This was caused by
+an x86-64 ABI conformance issue in some of libjpeg-turbo's 64-bit SSE2 SIMD
+routines.  Those routines were incorrectly using a 64-bit mov instruction to
+transfer a 32-bit JDIMENSION argument, whereas the x86-64 ABI allows the upper
+(unused) 32 bits of a 32-bit argument's register to be undefined.  The new
+Clang/LLVM optimizer uses load combining to transfer multiple adjacent 32-bit
+structure members into a single 64-bit register, and this exposed the ABI
+conformance issue.
+
 
 1.4.1
 =====
diff --git a/jmorecfg.h b/jmorecfg.h
index e86ccc60..8e3007c4 100644
--- a/jmorecfg.h
+++ b/jmorecfg.h
@@ -162,7 +162,9 @@ typedef long INT32;
  * images up to 64K*64K due to 16-bit fields in SOF markers.  Therefore
  * "unsigned int" is sufficient on all machines.  However, if you need to
  * handle larger images and you don't mind deviating from the spec, you
- * can change this datatype.
+ * can change this datatype.  (Note that changing this datatype will
+ * potentially require modifying the SIMD code.  The x86-64 SIMD extensions,
+ * in particular, assume a 32-bit JDIMENSION.)
  */
 
 typedef unsigned int JDIMENSION;
diff --git a/simd/jccolext-sse2-64.asm b/simd/jccolext-sse2-64.asm
index 7bd6d016..7ad43438 100644
--- a/simd/jccolext-sse2-64.asm
+++ b/simd/jccolext-sse2-64.asm
@@ -50,14 +50,14 @@ EXTN(jsimd_rgb_ycc_convert_sse2):
         collect_args
         push    rbx
 
-        mov     rcx, r10
+        mov     ecx, r10d
         test    rcx,rcx
         jz      near .return
 
         push    rcx
 
         mov rsi, r12
-        mov rcx, r13
+        mov ecx, r13d
         mov     rdi, JSAMPARRAY [rsi+0*SIZEOF_JSAMPARRAY]
         mov     rbx, JSAMPARRAY [rsi+1*SIZEOF_JSAMPARRAY]
         mov     rdx, JSAMPARRAY [rsi+2*SIZEOF_JSAMPARRAY]
diff --git a/simd/jcgryext-sse2-64.asm b/simd/jcgryext-sse2-64.asm
index 5af02e04..82c0fc81 100644
--- a/simd/jcgryext-sse2-64.asm
+++ b/simd/jcgryext-sse2-64.asm
@@ -50,14 +50,14 @@ EXTN(jsimd_rgb_gray_convert_sse2):
         collect_args
         push    rbx
 
-        mov     rcx, r10
+        mov     ecx, r10d
         test    rcx,rcx
         jz      near .return
 
         push    rcx
 
         mov rsi, r12
-        mov rcx, r13
+        mov ecx, r13d
         mov     rdi, JSAMPARRAY [rsi+0*SIZEOF_JSAMPARRAY]
         lea     rdi, [rdi+rcx*SIZEOF_JSAMPROW]
 
diff --git a/simd/jcsample-sse2-64.asm b/simd/jcsample-sse2-64.asm
index f32fb4fc..7693285c 100644
--- a/simd/jcsample-sse2-64.asm
+++ b/simd/jcsample-sse2-64.asm
@@ -49,11 +49,11 @@ EXTN(jsimd_h2v1_downsample_sse2):
         mov     rbp,rsp
         collect_args
 
-        mov rcx, r13
+        mov ecx, r13d
         shl     rcx,3                   ; imul rcx,DCTSIZE (rcx = output_cols)
         jz      near .return
 
-        mov rdx, r10
+        mov edx, r10d
 
         ; -- expand_right_edge
 
@@ -90,7 +90,7 @@ EXTN(jsimd_h2v1_downsample_sse2):
 
         ; -- h2v1_downsample
 
-        mov     rax, r12        ; rowctr
+        mov     eax, r12d        ; rowctr
         test    eax,eax
         jle     near .return
 
@@ -193,11 +193,11 @@ EXTN(jsimd_h2v2_downsample_sse2):
         mov     rbp,rsp
         collect_args
 
-        mov     rcx, r13
+        mov     ecx, r13d
         shl     rcx,3                   ; imul rcx,DCTSIZE (rcx = output_cols)
         jz      near .return
 
-        mov     rdx, r10
+        mov     edx, r10d
 
         ; -- expand_right_edge
 
@@ -234,7 +234,7 @@ EXTN(jsimd_h2v2_downsample_sse2):
 
         ; -- h2v2_downsample
 
-        mov     rax, r12        ; rowctr
+        mov     eax, r12d        ; rowctr
         test    rax,rax
         jle     near .return
 
diff --git a/simd/jdcolext-sse2-64.asm b/simd/jdcolext-sse2-64.asm
index bfd1f35d..d356e659 100644
--- a/simd/jdcolext-sse2-64.asm
+++ b/simd/jdcolext-sse2-64.asm
@@ -52,14 +52,14 @@ EXTN(jsimd_ycc_rgb_convert_sse2):
         collect_args
         push    rbx
 
-        mov     rcx, r10        ; num_cols
+        mov     ecx, r10d        ; num_cols
         test    rcx,rcx
         jz      near .return
 
         push    rcx
 
         mov     rdi, r11
-        mov     rcx, r12
+        mov     ecx, r12d
         mov     rsi, JSAMPARRAY [rdi+0*SIZEOF_JSAMPARRAY]
         mov     rbx, JSAMPARRAY [rdi+1*SIZEOF_JSAMPARRAY]
         mov     rdx, JSAMPARRAY [rdi+2*SIZEOF_JSAMPARRAY]
diff --git a/simd/jdmrgext-sse2-64.asm b/simd/jdmrgext-sse2-64.asm
index ff127b57..989d7f17 100644
--- a/simd/jdmrgext-sse2-64.asm
+++ b/simd/jdmrgext-sse2-64.asm
@@ -52,14 +52,14 @@ EXTN(jsimd_h2v1_merged_upsample_sse2):
         collect_args
         push    rbx
 
-        mov     rcx, r10        ; col
+        mov     ecx, r10d        ; col
         test    rcx,rcx
         jz      near .return
 
         push    rcx
 
         mov     rdi, r11
-        mov     rcx, r12
+        mov     ecx, r12d
         mov     rsi, JSAMPARRAY [rdi+0*SIZEOF_JSAMPARRAY]
         mov     rbx, JSAMPARRAY [rdi+1*SIZEOF_JSAMPARRAY]
         mov     rdx, JSAMPARRAY [rdi+2*SIZEOF_JSAMPARRAY]
@@ -455,10 +455,10 @@ EXTN(jsimd_h2v2_merged_upsample_sse2):
         collect_args
         push    rbx
 
-        mov     rax, r10
+        mov     eax, r10d
 
         mov     rdi, r11
-        mov     rcx, r12
+        mov     ecx, r12d
         mov     rsi, JSAMPARRAY [rdi+0*SIZEOF_JSAMPARRAY]
         mov     rbx, JSAMPARRAY [rdi+1*SIZEOF_JSAMPARRAY]
         mov     rdx, JSAMPARRAY [rdi+2*SIZEOF_JSAMPARRAY]
diff --git a/simd/jdsample-sse2-64.asm b/simd/jdsample-sse2-64.asm
index 335ce2aa..2287c00e 100644
--- a/simd/jdsample-sse2-64.asm
+++ b/simd/jdsample-sse2-64.asm
@@ -67,7 +67,7 @@ EXTN(jsimd_h2v1_fancy_upsample_sse2):
         mov     rbp,rsp
         collect_args
 
-        mov     rax, r11  ; colctr
+        mov     eax, r11d  ; colctr
         test    rax,rax
         jz      near .return
 
@@ -214,7 +214,7 @@ EXTN(jsimd_h2v2_fancy_upsample_sse2):
         collect_args
         push    rbx
 
-        mov     rax, r11  ; colctr
+        mov     eax, r11d  ; colctr
         test    rax,rax
         jz      near .return
 
@@ -506,7 +506,7 @@ EXTN(jsimd_h2v1_upsample_sse2):
         mov     rbp,rsp
         collect_args
 
-        mov     rdx, r11
+        mov     edx, r11d
         add     rdx, byte (2*SIZEOF_XMMWORD)-1
         and     rdx, byte -(2*SIZEOF_XMMWORD)
         jz      near .return
@@ -596,7 +596,7 @@ EXTN(jsimd_h2v2_upsample_sse2):
         collect_args
         push    rbx
 
-        mov     rdx, r11
+        mov     edx, r11d
         add     rdx, byte (2*SIZEOF_XMMWORD)-1
         and     rdx, byte -(2*SIZEOF_XMMWORD)
         jz      near .return
diff --git a/simd/jidctflt-sse2-64.asm b/simd/jidctflt-sse2-64.asm
index 32e4ec22..95bd4dcd 100644
--- a/simd/jidctflt-sse2-64.asm
+++ b/simd/jidctflt-sse2-64.asm
@@ -326,7 +326,7 @@ EXTN(jsimd_idct_float_sse2):
         mov     rax, [original_rbp]
         lea     rsi, [workspace]                        ; FAST_FLOAT * wsptr
         mov     rdi, r12        ; (JSAMPROW *)
-        mov     rax, r13
+        mov     eax, r13d
         mov     rcx, DCTSIZE/4                          ; ctr
 .rowloop:
 
diff --git a/simd/jidctfst-sse2-64.asm b/simd/jidctfst-sse2-64.asm
index bcc3e3a6..0f864291 100644
--- a/simd/jidctfst-sse2-64.asm
+++ b/simd/jidctfst-sse2-64.asm
@@ -323,7 +323,7 @@ EXTN(jsimd_idct_ifast_sse2):
 
         mov     rax, [original_rbp]
         mov     rdi, r12        ; (JSAMPROW *)
-        mov     rax, r13
+        mov     eax, r13d
 
         ; -- Even part
 
diff --git a/simd/jidctint-sse2-64.asm b/simd/jidctint-sse2-64.asm
index 32bbfd8d..1cc30866 100644
--- a/simd/jidctint-sse2-64.asm
+++ b/simd/jidctint-sse2-64.asm
@@ -515,7 +515,7 @@ EXTN(jsimd_idct_islow_sse2):
 
         mov     rax, [original_rbp]
         mov     rdi, r12        ; (JSAMPROW *)
-        mov     rax, r13
+        mov     eax, r13d
 
         ; -- Even part
 
diff --git a/simd/jidctred-sse2-64.asm b/simd/jidctred-sse2-64.asm
index dad43d90..02b155a8 100644
--- a/simd/jidctred-sse2-64.asm
+++ b/simd/jidctred-sse2-64.asm
@@ -312,7 +312,7 @@ EXTN(jsimd_idct_4x4_sse2):
 
         mov     rax, [original_rbp]
         mov     rdi, r12        ; (JSAMPROW *)
-        mov     rax, r13
+        mov     eax, r13d
 
         ; -- Even part
 
@@ -521,7 +521,7 @@ EXTN(jsimd_idct_2x2_sse2):
         ; ---- Pass 2: process rows, store into output array.
 
         mov     rdi, r12        ; (JSAMPROW *)
-        mov     rax, r13
+        mov     eax, r13d
 
         ; | input:| result:|
         ; | A0 B0 |        |
diff --git a/simd/jquantf-sse2-64.asm b/simd/jquantf-sse2-64.asm
index 20e815f7..cf7f0d82 100644
--- a/simd/jquantf-sse2-64.asm
+++ b/simd/jquantf-sse2-64.asm
@@ -50,7 +50,7 @@ EXTN(jsimd_convsamp_float_sse2):
         packsswb xmm7,xmm7              ; xmm7 = PB_CENTERJSAMPLE (0x808080..)
 
         mov rsi, r10
-        mov     rax, r11
+        mov     eax, r11d
         mov rdi, r12
         mov     rcx, DCTSIZE/2
 .convloop:
diff --git a/simd/jquanti-sse2-64.asm b/simd/jquanti-sse2-64.asm
index 50b8dce7..b61f4db2 100644
--- a/simd/jquanti-sse2-64.asm
+++ b/simd/jquanti-sse2-64.asm
@@ -50,7 +50,7 @@ EXTN(jsimd_convsamp_sse2):
         psllw   xmm7,7                  ; xmm7={0xFF80 0xFF80 0xFF80 0xFF80 ..}
 
         mov rsi, r10
-        mov rax, r11
+        mov eax, r11d
         mov rdi, r12
         mov     rcx, DCTSIZE/4
 .convloop: